Document:

<PAGE>   1
                                                                   EXHIBIT 10.18

                       PREFERRED STOCK EXCHANGE AGREEMENT

         This Preferred Stock Exchange Agreement (this "Agreement"), effective
as of January ___, 2001, is by and between TELESCAN, INC., a Delaware
corporation (the "Company"), and R2 FUNDING, LTD., a Cayman Islands Exempted
Company (the "Investor").

         WHEREAS, Investor is the owner of 60,000 shares of Class A 5%
Convertible Preferred Stock (the "Class A Preferred Stock"), of the Company; and

         WHEREAS, Investor and the Company have agreed to exchange such shares
of Class A Preferred Stock for a new class of preferred stock from the Company
entitled "Class B 4% Convertible Preferred Stock" pursuant to a
"recapitalization" within the meaning of Section 368(a)(1)(E) of the Internal
Revenue Code of 1986, as amended.

         NOW, THEREFORE, in consideration of the premises and the agreements
herein set forth and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto, intending to
be legally bound hereby, agree as follows:

         1. Return of Class A Preferred Stock and Cancellation; Exchange for
Class B Preferred Stock. On the date hereof, Investor shall deliver the
certificate representing its shares of Class A Preferred Stock to the Company.
In exchange for Investor's delivery of the certificate representing its shares
of Class A Preferred Stock, the Company shall issue and deliver to Investor
60,000 shares of the Company's Class B 4% Convertible Preferred Stock (the
"Shares" or "Convertible Preferred") having the rights, designations and
preferences set forth in Schedule I hereto.

         2. Release of Claims. Investor hereby waives any claims and rights
which it ever had, now has or hereafter can, shall or may have against the
Company arising out of, relating to or in connection with the acquisition or
ownership of the Class A Preferred Stock.

         3. Representations and Warranties of the Investor. Investor hereby
makes the following representations and warranties to the Company:

                  (a) Authorization, Enforcement. (i) Investor has the requisite
power and authority to enter into and perform this Agreement and to acquire the
Shares hereunder, (ii) the execution and delivery of this Agreement by Investor
and the consummation by it of the transactions contemplated hereby have been
duly authorized by all necessary partnership action, and (iii) this Agreement
constitutes a valid and binding obligation of Investor enforceable against
Investor in accordance with its terms except as such enforceability may be
limited by applicable bankruptcy, insolvency, reorganization, moratorium,
liquidation or similar laws relating to, or affecting generally the enforcement
of, creditors' rights and remedies or by other equitable principles of general
application.

                  (b) No Conflicts. The execution, delivery and performance of
this Agreement and the consummation by Investor of the transactions contemplated
hereby do not and will not

<PAGE>   2

(i) result in a violation of Investor's organizational documents , (ii) conflict
with any agreement, indenture or instrument to which Investor is a party, or
(iii) result in a violation of any law, rule, or regulation, or any order,
judgment or decree of any court or governmental agency applicable to Investor.
Investor is not required to obtain any consent or authorization of any
governmental agency in order for it to perform its obligations under this
Agreement

                  (c) Status of Class A Preferred Stock and Investor. Investor
is not, and never has been, an "affiliate" of the Company (as such term is
defined in the Securities Act of 1933, as amended (the "Act"), and the rules
thereunder) and has held the shares of Class A Preferred Stock for more than two
years as prescribed by, and in accordance with, Rule 144 under the Act.

         4. Representations and Warranties of the Company. The Company hereby
makes the following representations and warranties to Investor:

                  (a) Organization and Qualification. The Company is a
corporation duly incorporated and existing in good standing under the laws of
the State of Delaware and has the requisite corporate power to own its
properties and to carry on its business as now being conducted. The Company does
not have any subsidiaries except as listed in Exhibit A hereto. The Company and
each such subsidiary, if any, is duly qualified as a foreign corporation to do
business and is in good standing in every jurisdiction in which the nature of
the business conducted or property owned by it makes such qualification
necessary other than those in which the failure so to qualify would not have a
Material Adverse Effect. "Material Adverse Effect" means any adverse effect on
the business, operations, properties, prospects, or financial condition of the
entity with respect to which such term is used and which is material to such
entity and other entities controlled by such entity taken as a whole.

                  (b) Authorization; Enforcement. (i) The Company has the
requisite corporate power and authority to enter into and perform this Agreement
and to issue the Shares in accordance with the terms hereof, (ii) the execution
and delivery of this Agreement by the Company and the consummation by it of the
transactions contemplated hereby have been duly authorized by all necessary
corporate action, and no further consent or authorization of the Company or its
Board of Directors or stockholders is required except for any stockholder
approval required by the terms of the Company's listing agreement with Nasdaq or
the rules of such organization, (iii) this Agreement has been duly executed and
delivered by the Company, (iv) this Agreement constitutes a valid and binding
obligation of the Company enforceable against the Company in accordance with its
terms, except as such enforceability may be limited by applicable bankruptcy,
insolvency, reorganization, moratorium, liquidation or similar laws relating to,
or affecting generally the enforcement of, creditors' rights and remedies or by
other equitable principles of general application, and (v) prior to the date
hereof a Certificate of Designations which authorizes the Convertible Preferred
as provided in Schedule I will have been filed with the Delaware Secretary of
State and will be in full force and effect, enforceable against the Company in
accordance with its terms.

                  (c) Capitalization. The authorized capital stock of the
Company consists of 30,000,000 shares of Common Stock and 10,000,000 shares of
preferred stock; there are

                                       2
<PAGE>   3

approximately 16,296,026 shares of Common Stock and 120,000 shares of Class A
Preferred Stock issued and outstanding; and, upon issuance of the Shares in
accordance with the terms hereof and pursuant to similar agreements of like
tenor, there will be approximately 16,296,026 shares of Common Stock and 120,000
shares of Class B 4% Convertible Preferred Stock issued and outstanding. All of
the outstanding shares of the Company's capital stock have been validly issued
and are fully paid and nonassessable. Except as set forth in Exhibit A hereto
and as described in the SEC Documents (as hereinafter defined), no shares of
Common Stock are entitled to preemptive rights or registration rights and there
are no outstanding options, warrants, scrip, rights to subscribe to, calls or
commitments of any character whatsoever relating to, or securities or rights
convertible into, any shares of capital stock of the Company, or contracts,
commitments, understandings, or arrangements by which the Company is or may
become bound to issue additional shares of capital stock of the Company or
options, warrants, scrip, rights to subscribe to, or commitments to purchase or
acquire, any shares, or securities or rights convertible into shares, of capital
stock of the Company. The Company has furnished or made available to the
Investor true and correct copies of the Company's Certificate of Incorporation
as in effect on the date hereof (the "Charter"), and the Company's By-Laws, as
in effect on the date hereof (the "By-Laws").

                  (d) Issuance of Shares. The issuance of the Shares has been
duly authorized and, when paid for and issued in accordance with the terms
hereof, the Shares shall be validly issued, fully paid and non-assessable and
entitled to the rights and preferences set forth in Schedule I hereto. The
Company shall have authorized and reserved for issuance upon conversion of the
Class B 4% Convertible Preferred Stock 3,000,000 shares of Common Stock (the
"Reserved Amount"), which number shall not be reduced, but which shall be
appropriately adjusted by the Board of Directors, acting in good faith, in the
event of stock splits, dividends or other distributions, or other events so as
to carry out the intentions of this Agreement. If the Reserved Amount for any
three consecutive trading days shall be less than 125% of the number of shares
of Common Stock issuable upon conversion of the Convertible Preferred, the
Company shall immediately notify all holders of the Convertible Preferred of
such occurrence and shall take action as soon as possible, but in any event
within 60 days (including, if necessary, seeking shareholder approval to
authorize the issuance of additional shares of Common Stock) to increase the
Reserved Amount to 200% of the number of shares of Common Stock then issuable
upon conversion of the Convertible Preferred. The Common Stock issuable upon
conversion of the Convertible Preferred will be duly authorized, validly issued,
fully paid and nonassessable and the holders shall be entitled to all rights and
preferences accorded to a holder of Common Stock.

                  (e) No Conflicts. The execution, delivery and performance of
this Agreement by the Company and the consummation by the Company of the
transactions contemplated hereby do not and will not (i) result in a violation
of the Company's Charter or By-Laws or (ii) conflict with, or constitute a
default (or an event which with notice or lapse of time or both would become a
default) under, or give to others any rights of termination, amendment,
acceleration or cancellation of, any agreement, indenture or instrument to which
the Company or any of its subsidiaries is a party, or result in a violation of
any federal, state, local or foreign law, rule, regulation, order, judgment or
decree (including Federal and state securities laws and

                                       3
<PAGE>   4

regulations) applicable to the Company or any of its subsidiaries or by which
any property or assets of the Company or any of its subsidiaries is bound or
affected (except for such conflicts, defaults, terminations, amendments,
accelerations, cancellations and violations as would not, individually or in the
aggregate, have a Material Adverse Effect); provided that, for purposes of such
representation as to Federal, state, local or foreign law, rule or regulation,
no representation is made herein with respect to any of the same applicable
solely to the Investor and not to the Company. The business of the Company is
not being conducted in violation of any law, ordinance or regulation of any
governmental entity, except for violations which either singly or in the
aggregate do not and will not have a Material Adverse Effect. The Company is not
required under Federal, state or local law, rule or regulation in the United
States to obtain any consent, authorization or order of, or make any filing
(other than the filing of the Certificate of Amendment with the Delaware
Secretary of State) or registration with, any court or governmental agency in
order for it to execute, deliver or perform any of its obligations under this
Agreement or issue and sell the Shares in accordance with the terms hereof
(other than any SEC, NASD, stock exchange or state securities filings which may
be required to be made by the Company subsequent to the Closing, and any
registration statement which may be filed pursuant hereto); provided that, for
purposes of the representation made in this sentence, the Company is assuming
and relying upon the accuracy of the relevant representations and agreements of
the Investor herein.

                  (f) SEC Documents, Financial Statements. The Common Stock of
the Company is registered pursuant to Section 12(b) or Section 12(g) of the
Securities Exchange Act of 1934, as amended (the "Exchange Act") and the Company
has filed on a timely basis all reports, schedules, forms, statements and other
documents required to be filed by it with the SEC since January 1, 1997 pursuant
to the reporting requirements of the Exchange Act, including material filed
pursuant to Section 13(a) or 15(d), in addition to one or more registration
statements and amendments thereto heretofore filed by the Company with the SEC
under the Act since July 1, 1996 (all of the foregoing including filings
incorporated by reference therein being referred to herein as the "SEC
Documents"). The Company has delivered or made available to the Investor true
and complete copies of the SEC Documents. The Company has not provided to the
Investor any information which, according to applicable law, rule or regulation,
should have been disclosed publicly by the Company but which has not been so
disclosed, other than with respect to the transactions contemplated by this
Agreement. As of their respective dates, the SEC Documents complied in all
material respects with the requirements of the Act or the Exchange Act as the
case may be and the rules and regulations of the SEC promulgated thereunder and
other federal, state and local laws, rules and regulations applicable to such
SEC Documents, and none of the SEC Documents contained any untrue statement of a
material fact or omitted to state a material fact required to be stated therein
or necessary in order to make the statements therein, in light of the
circumstances under which they were made, not misleading. The financial
statements of the Company included in the SEC Documents comply as to form in all
material respects with applicable accounting requirements and the published
rules and regulations of the SEC or other applicable rules and regulations with
respect thereto. Such financial statements have been prepared in accordance with
generally accepted accounting principles applied on a consistent basis during
the periods involved (except as may be otherwise indicated in such financial
statements or the notes thereto) and fairly present in all material

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<PAGE>   5

respects the financial position of the Company as of the dates thereof and the
results of operations and cash flows for the periods then ended (subject, in the
case of unaudited statements, to normal year-end audit adjustments).

                  (g) No Material Adverse Change. Since the date through which
the most recent report of the Company on Form 10-K or Form 10-Q has been
prepared and filed with the SEC, a copy of which is included in the SEC
Documents, no Material Adverse Effect has occurred or exists with respect to the
Company or its subsidiaries.

                  (h) No Undisclosed Liabilities. The Company and its
subsidiaries have no material liabilities or obligations not disclosed in the
SEC Documents, other than those incurred in the ordinary course of the Company's
or its subsidiaries' respective businesses since the date of the most recently
filed SEC Documents which, individually or in the aggregate, do not or would not
have a Material Adverse Effect on the Company or its subsidiaries.

                  (i) No Undisclosed Events or Circumstances. To the best
knowledge of the Company, no event or circumstance has occurred or exists with
respect to the Company or its subsidiaries or their respective businesses,
properties, prospects, operations or financial condition, which, under
applicable law, rule or regulation, requires public disclosure or announcement
by the Company but which has not been so publicly announced or disclosed.

                  (j) Freely Tradeable Shares. The Shares issued hereunder are
freely tradeable without restrictions as to timing or amount or otherwise and
are unlegended (except as respects Delaware law concerning preferred stock).

         5. Fees and Expenses. Each party shall pay the fees and expenses of its
advisers, counsel, accountants and other experts, if any, and all other expenses
incurred by such party incident to the negotiation, preparation, execution,
delivery and performance of this Agreement. The Company shall pay all stamp and
other taxes and duties levied in connection with the issuance of the Shares
pursuant hereto.

         6. Entire Agreement, Amendment. This Agreement contains the entire
understanding of the parties with respect to the matters covered hereby and,
except as specifically set forth herein, neither the Company nor Investor makes
any representation, warranty, covenant or undertaking with respect to such
matters. No provision of this Agreement may be waived or amended other than by a
written instrument signed by the party against whom enforcement of any such
amendment or waiver is sought.

         7. Notices. Any notice or other communication required or permitted to
be given hereunder shall be in writing and shall be effective (a) upon hand
delivery or delivery by telex (with correct answer back received), telecopy or
facsimile at the address or number designated below (if delivered on a business
day during normal business hours where such notice is to be received), or the
first business day following such delivery (if delivered other than on a
business day during normal business hours where such notice is to be received)
or (b) on the second business day following the date of mailing by express
courier service, fully prepaid, addressed to

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<PAGE>   6

such address, or upon actual receipt of such mailing, whichever shall first
occur. The addresses for such communications shall be:

                  to the Company:   Roger C. Wadsworth
                                    Senior Vice President
                                    Telescan, Inc.
                                    5959 Corporate Drive, Suite 2000
                                    Houston, Texas 77036

                  with copies to:   David F. Taylor
                                    Locke Liddell & Sapp LLP
                                    600 Travis, 32nd Floor
                                    Houston, Texas 77002-3095

                  to the Investor:  At the address set forth at the foot of this
                                    Agreement

         Any party hereto may from time to time change its address for notices
by giving at least 10 days' written notice of such changed address to the other
party hereto.

         8. Headings. The headings herein are for convenience only, do not
constitute a part of this Agreement and shall not be deemed to limit or affect
any of the provisions hereof.

         9. Successors and Assigns. Except as otherwise provided herein, this
Agreement shall be binding upon and inure to the benefit of the parties and
their successors and assigns. The parties hereto may amend this Agreement
without notice to or the consent of any third party. The assignment by a party
to this Agreement of any rights hereunder shall not affect the obligations of
such party under this Agreement.

         10. No Third Party Beneficiaries. This Agreement is intended for the
benefit of the parties hereto and their respective permitted successors and
assigns and is not for the benefit of, nor may any provision hereof be enforced
by, any other person.

         11. Governing Law. This Agreement shall be governed by and construed
and enforced in accordance with the internal laws of Texas without regard to
such state's principles of conflict of laws.

         12. Survival. The representations and warranties of the Company and
Investor contained in Sections 3 and 4 and shall survive the Closing.

         13. Execution. This Agreement may be executed in two or more
counterparts, all of which shall be considered one and the same agreement and
shall become effective when counterparts have been signed by each party and
delivered to the other party, it being understood that both parties need not
sign the same counterpart. In the event any signature is delivered by facsimile
transmission, the party using such means of delivery shall cause the manually
executed signature page(s) to be physically delivered to the other party within
five days of the execution hereof.

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<PAGE>   7

         14. Publicity. The Company agrees that it will not disclose, and will
not include in any public announcement, the name of the Investor without its
consent, unless and until such disclosure is required by law or applicable
regulation, and then only to the extent of such requirement.

         IN WITNESS WHEREOF, the undersigned have executed this Agreement
effective as of the date first written above.

                                         TELESCAN, INC.

                                         By:
                                            ------------------------------------
                                         Name:
                                              ----------------------------------
                                         Title:
                                               ---------------------------------

                                         R(2) FUNDING, LTD.

                                         By: Amalgamated Gadget, L.P., as
                                             Investment Manager

                                             By: Scepter Holdings, Inc., general
                                                 partner

                                             By:
                                                --------------------------------
                                                Geoffrey Raynor, President

                                         Address:

                                         c/o Amalgamated Gadget, L.P.,
                                             as Investment Manager
                                             Attn: Geoffrey Raynor
                                             301 Commerce Street, Suite 2975
                                             Fort Worth, Texas  76102

                                       7<PAGE>   1
                                                                    EXHIBIT 4.11

                            NABORS INDUSTRIES, INC.,
                                   as Issuer,

                             ZERO COUPON CONVERTIBLE
                           SENIOR DEBENTURES DUE 2021

                          ----------------------------

                                    INDENTURE

                          Dated as of February 5, 2001

                          ----------------------------

                                 Bank One, N.A.,

                                   as Trustee

                          ----------------------------

<PAGE>   2

                             CROSS REFERENCE TABLE*

<TABLE>
<CAPTION>
TIA                                                                                                    INDENTURE
SECTION                                                                                                  SECTION
-------                                                                                               ----------
<S>                                                                                                   <C>

  3.10        (a)(1)  .............................................................................         7.10
              (a)(2)  .............................................................................         7.10
              (a)(3)  .............................................................................       N.A.**
              (a)(4)  .............................................................................         N.A.
                 (b)  .............................................................................   7.08; 7.10
                 (c)  .............................................................................         N.A.
  3.11           (a)  .............................................................................         7.11
                 (b)  .............................................................................         7.11
                 (c)  .............................................................................         N.A.
  3.12           (a)  .............................................................................         2.05
                 (b)  .............................................................................        13.03
                 (c)  .............................................................................        13.03
                 (d)  .............................................................................         7.06
  3.13           (a)  .............................................................................         7.06
              (b)(1)  .............................................................................         N.A.
              (b)(2)  .............................................................................         7.06
                 (c)  .............................................................................        13.02
                 (d)  .............................................................................         7.06
  3.14           (a)  .............................................................................  4.02; 13.02
                 (b)  .............................................................................         N.A.
              (c)(1)  .............................................................................        13.04
              (c)(2)  .............................................................................        13.04
              (c)(3)  .............................................................................         N.A.
                 (d)  .............................................................................         N.A.
                 (e)  .............................................................................        13.05
                 (f)  .............................................................................         4.03
  3.15           (a)  .............................................................................         7.01
                 (b)  .............................................................................  7.05; 13.02
                 (c)  .............................................................................         7.01
                 (d)  .............................................................................         7.01
                 (e)  .............................................................................         6.11
  3.16           (a)  (last sentence)..............................................................         2.08
           (a)(1)(A)  .............................................................................         6.05
           (a)(1)(B)  .............................................................................         6.04
              (a)(2)  .............................................................................         N.A.
                 (b)  .............................................................................         6.07
  3.17        (a)(1)  .............................................................................         6.08
              (a)(2)  .............................................................................         6.09
                 (b)  .............................................................................         2.04
  3.18           (a)  .............................................................................        13.01
</TABLE>

*   Note: This Cross Reference Table shall not, for any purpose, be deemed to be
          part of the Indenture.

**  Note: N.A. means Not Applicable.

<PAGE>   3

                               TABLE OF CONTENTS
<TABLE>
<CAPTION>
                                                                                                                      PAGE
<S>                                                                                                                   <C>
ARTICLE 1.  DEFINITIONS AND INCORPORATION BY REFERENCE............................................................      1
   SECTION 1.01. DEFINITIONS......................................................................................      1
   SECTION 1.02. OTHER DEFINITIONS................................................................................      6
   SECTION 1.03. INCORPORATION BY REFERENCE OF TRUST INDENTURE ACT................................................      7
   SECTION 1.04. RULES OF CONSTRUCTION............................................................................      7
ARTICLE 2.  THE SECURITIES........................................................................................      8
   SECTION 2.01. FORM AND DATING..................................................................................      8
   SECTION 2.02. EXECUTION AND AUTHENTICATION.....................................................................      8
   SECTION 2.03. REGISTRAR, PAYING AGENT AND CONVERSION AGENT.....................................................      9
   SECTION 2.04. PAYING AGENT TO HOLD CASH AND SECURITIES IN TRUST................................................      9
   SECTION 2.05. HOLDER LISTS.....................................................................................     10
   SECTION 2.06. EXCHANGE AND REGISTRATION OF TRANSFER OF SECURITIES; RESTRICTIONS ON TRANSFERS; DEPOSITARY.......     10
   SECTION 2.07. REPLACEMENT SECURITIES...........................................................................     15
   SECTION 2.08. OUTSTANDING SECURITIES; DETERMINATIONS OF HOLDERS' ACTION........................................     15
   SECTION 2.09. TEMPORARY SECURITIES.............................................................................     16
   SECTION 2.10. CANCELLATION.....................................................................................     17
   SECTION 2.11. PERSONS DEEMED OWNERS............................................................................     17
   SECTION 2.12. CUSIP NUMBERS....................................................................................     17
ARTICLE 3.  REDEMPTION AND REPURCHASES............................................................................     17
   SECTION 3.01. RIGHT TO REDEEM; NOTICES TO TRUSTEE..............................................................     17
   SECTION 3.02. SELECTION OF SECURITIES TO BE REDEEMED...........................................................     18
   SECTION 3.03. NOTICE OF REDEMPTION.............................................................................     18
   SECTION 3.04. EFFECT OF NOTICE OF REDEMPTION...................................................................     19
   SECTION 3.05. DEPOSIT OF REDEMPTION PRICE......................................................................     20
   SECTION 3.06. SECURITIES REDEEMED IN PART......................................................................     20
   SECTION 3.07. CONVERSION ARRANGEMENT ON CALL FOR REDEMPTION....................................................     20
   SECTION 3.08. REPURCHASE OF SECURITIES AT OPTION OF THE HOLDER.................................................     21
   SECTION 3.09. REPURCHASE AT OPTION OF THE HOLDER UPON A FUNDAMENTAL CHANGE.....................................     26
   SECTION 3.10. EFFECT OF REPURCHASE NOTICE OR FUNDAMENTAL CHANGE REPURCHASE NOTICE..............................     27
   SECTION 3.11. DEPOSIT OF PURCHASE PRICE OR FUNDAMENTAL CHANGE PURCHASE PRICE...................................     28
   SECTION 3.12. SECURITIES REPURCHASED IN PART...................................................................     29
   SECTION 3.13. COVENANT TO COMPLY WITH SECURITIES LAWS UPON REPURCHASE OF SECURITIES............................     29
   SECTION 3.14. REPAYMENT TO THE COMPANY.........................................................................     29
ARTICLE 4.  COVENANTS.............................................................................................     29
   SECTION 4.01. PAYMENT OF SECURITIES............................................................................     29
   SECTION 4.02. FINANCIAL INFORMATION; SEC REPORTS...............................................................     30
</TABLE>

                                      -i-
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<TABLE>
<S>                                                                                                                   <C>

   SECTION 4.03. COMPLIANCE CERTIFICATE...........................................................................     31
   SECTION 4.04. FURTHER INSTRUMENTS AND ACTS.....................................................................     31
   SECTION 4.05. MAINTENANCE OF OFFICE OR AGENCY..................................................................     31
   SECTION 4.06. EXISTENCE........................................................................................     32
   SECTION 4.07. CALCULATION OF ORIGINAL ISSUE DISCOUNT...........................................................     32
   SECTION 4.08. REGISTRATION RIGHTS..............................................................................     32
ARTICLE 5.  SUCCESSOR CORPORATION.................................................................................     33
   SECTION 5.01. WHEN THE COMPANY MAY MERGE OR TRANSFER ASSETS....................................................     33
ARTICLE 6.  DEFAULTS AND REMEDIES.................................................................................     34
   SECTION 6.01. EVENTS OF DEFAULT................................................................................     34
   SECTION 6.02. ACCELERATION.....................................................................................     35
   SECTION 6.03. OTHER REMEDIES...................................................................................     35
   SECTION 6.04. WAIVER OF PAST DEFAULTS..........................................................................     36
   SECTION 6.05. CONTROL BY MAJORITY..............................................................................     36
   SECTION 6.06. LIMITATION ON SUITS..............................................................................     36
   SECTION 6.07. RIGHTS OF HOLDERS TO RECEIVE PAYMENT.............................................................     37
   SECTION 6.08. COLLECTION SUIT BY TRUSTEE.......................................................................     37
   SECTION 6.09. TRUSTEE MAY FILE PROOFS OF CLAIM.................................................................     37
   SECTION 6.10. PRIORITIES.......................................................................................     38
   SECTION 6.11. UNDERTAKING FOR COSTS............................................................................     38
   SECTION 6.12. WAIVER OF STAY, EXTENSION OR USURY LAWS..........................................................     39
ARTICLE 7.  TRUSTEE...............................................................................................     39
   SECTION 7.01. DUTIES OF TRUSTEE................................................................................     39
   SECTION 7.02. RIGHTS OF TRUSTEE................................................................................     40
   SECTION 7.03. INDIVIDUAL RIGHTS OF TRUSTEE.....................................................................     42
   SECTION 7.04. TRUSTEE'S DISCLAIMER.............................................................................     42
   SECTION 7.05. NOTICE OF DEFAULTS...............................................................................     42
   SECTION 7.06. REPORTS BY TRUSTEE TO HOLDERS....................................................................     42
   SECTION 7.07. COMPENSATION AND INDEMNITY.......................................................................     42
   SECTION 7.08. REPLACEMENT OF TRUSTEE...........................................................................     43
   SECTION 7.09. SUCCESSOR TRUSTEE BY MERGER......................................................................     44
   SECTION 7.10. ELIGIBILITY; DISQUALIFICATION....................................................................     45
   SECTION 7.11. PREFERENTIAL COLLECTION OF CLAIMS AGAINST COMPANY................................................     45
ARTICLE 8.  DISCHARGE OF INDENTURE................................................................................     45
   SECTION 8.01. DISCHARGE OF LIABILITY ON SECURITIES.............................................................     45
   SECTION 8.02. REPAYMENT TO THE COMPANY.........................................................................     45
ARTICLE 9.  AMENDMENTS............................................................................................     46
   SECTION 9.01. WITHOUT CONSENT OF HOLDERS.......................................................................     46
   SECTION 9.02. WITH CONSENT OF HOLDERS..........................................................................     46
   SECTION 9.03. COMPLIANCE WITH TRUST INDENTURE ACT..............................................................     47
   SECTION 9.04. REVOCATION AND EFFECT OF CONSENTS, WAIVERS AND ACTIONS...........................................     47
   SECTION 9.05. NOTATION ON OR EXCHANGE OF SECURITIES............................................................     48
   SECTION 9.06. TRUSTEE TO SIGN SUPPLEMENTAL INDENTURES..........................................................     48
   SECTION 9.07. EFFECT OF SUPPLEMENTAL INDENTURES................................................................     48
ARTICLE 10. [INTENTIONALLY OMITTED]...............................................................................     48
</TABLE>

                                  -ii-
<PAGE>   5

<TABLE>
<S>                                                                                                                   <C>
ARTICLE 11.  CONVERSION...........................................................................................     48
   SECTION 11.01. CONVERSION PRIVILEGE............................................................................     48
   SECTION 11.02. CONVERSION PROCEDURE............................................................................     49
   SECTION 11.03. FRACTIONAL SHARES...............................................................................     50
   SECTION 11.04. TAXES ON CONVERSION.............................................................................     51
   SECTION 11.05. COMPANY TO PROVIDE STOCK........................................................................     51
   SECTION 11.06. ADJUSTMENT FOR CHANGE IN CAPITAL STOCK..........................................................     52
   SECTION 11.07. ADJUSTMENT FOR RIGHTS OR WARRANTS...............................................................     52
   SECTION 11.08. ADJUSTMENT FOR OTHER DISTRIBUTIONS..............................................................     53
   SECTION 11.09. WHEN ADJUSTMENT MAY BE DEFERRED.................................................................     54
   SECTION 11.10. WHEN NO ADJUSTMENT REQUIRED.....................................................................     55
   SECTION 11.11. NOTICE OF ADJUSTMENT............................................................................     55
   SECTION 11.12. VOLUNTARY CHANGE................................................................................     55
   SECTION 11.13. NOTICE OF CERTAIN TRANSACTIONS..................................................................     55
   SECTION 11.14. EFFECT OF RECLASSIFICATION, CONSOLIDATION, MERGER OR SALE.......................................     56
   SECTION 11.15. COMPANY DETERMINATION FINAL.....................................................................     57
   SECTION 11.16. TRUSTEE'S ADJUSTMENT DISCLAIMER.................................................................     57
   SECTION 11.17. SIMULTANEOUS ADJUSTMENTS........................................................................     57
   SECTION 11.18. SUCCESSIVE ADJUSTMENTS..........................................................................     57
   SECTION 11.19. RIGHTS ISSUED IN RESPECT OF COMMON STOCK ISSUED UPON CONVERSION.................................     57
   SECTION 11.20. GENERAL CONSIDERATIONS..........................................................................     58
ARTICLE 12.  SPECIAL TAX EVENT....................................................................................     58
   SECTION 12.01. OPTIONAL CONVERSION TO SEMIANNUAL COUPON DEBENTURE UPON TAX EVENT...............................     58
   SECTION 12.02. PAYMENT OF INTEREST; INTEREST RIGHTS PRESERVED..................................................     59
ARTICLE 13.  MISCELLANEOUS 60
   SECTION 13.01. TRUST INDENTURE ACT.............................................................................     60
   SECTION 13.02. NOTICES.........................................................................................     61
   SECTION 13.03. COMMUNICATION BY HOLDERS WITH OTHER HOLDERS.....................................................     61
   SECTION 13.04. CERTIFICATE AND OPINION AS TO CONDITIONS PRECEDENT..............................................     62
   SECTION 13.05. STATEMENTS REQUIRED IN CERTIFICATE OR OPINION...................................................     62
   SECTION 13.06. SEPARABILITY CLAUSE.............................................................................     62
   SECTION 13.07. RULES BY TRUSTEE, PAYING AGENT, CONVERSION AGENT AND REGISTRAR..................................     62
   SECTION 13.08. GOVERNING LAW...................................................................................     63
   SECTION 13.09. NO RECOURSE AGAINST OTHERS......................................................................     63
   SECTION 13.10. RECORD DATE FOR VOTE OR CONSENT OF SECURITYHOLDERS..............................................     63
   SECTION 13.11. RULES BY TRUSTEE, PAYING AGENT, REGISTRAR.......................................................     63
   SECTION 13.12. SUCCESSORS......................................................................................     63
   SECTION 13.13. MULTIPLE ORIGINALS..............................................................................     63
</TABLE>
                                     -iii-
<PAGE>   6

EXHIBIT A -- Form of Security
EXHIBIT B -- Form of Institutional Accredited Investor Letter

                                      -iv-

<PAGE>   7

         INDENTURE, dated as of February 5, 2001, between Nabors Industries,
Inc., a Delaware corporation (the "COMPANY"), and Bank One, N.A., a national
banking association, as trustee (the "TRUSTEE").

         Each party agrees as follows for the benefit of the other parties and
for the equal and ratable benefit of the Holders of the Company's Zero Coupon
Convertible Senior Debentures due 2021:

                                   ARTICLE 1.
                   DEFINITIONS AND INCORPORATION BY REFERENCE

         SECTION 1.01. DEFINITIONS.

         "AFFILIATE" of any specified Person means any other Person directly or
indirectly controlling or controlled by or under direct or indirect common
control with such specified Person. For the purposes of this definition,
"control," when used with respect to any specified Person, means the power to
direct or cause the direction of the management and policies of such Person,
directly or indirectly, whether through the ownership of voting securities, by
contract or otherwise; and the terms "controlling" and "controlled" have
meanings correlative to the foregoing.

         "AMEX" means the American Stock Exchange.

         "BANKRUPTCY LAW" means Title 11, United States Code, or any similar
Federal or state law for the relief of debtors.

         "BOARD OF DIRECTORS" means either the board of directors of the Company
or any duly authorized committee of such board.

         "BUSINESS DAY" means each day of the year on which banking institutions
are not required or authorized to close in The City of New York, Houston, Texas
or the city in which the Corporate Trust Office is located.

         "COMMON STOCK" means any stock of any class of the Company which has no
preference in respect of dividends or of amounts payable in the event of any
voluntary or involuntary liquidation, dissolution or winding up of the Company
and which is not subject to redemption by the Company. Subject to the provisions
of Section 11.14 hereof, however, shares issuable upon conversion of the
Securities shall include only shares of Common Stock, par value of $.10 per
share, of the Company as such class of shares exists on the date of this
Indenture or shares of any class or classes resulting from any reclassification
or reclassifications thereof and which have no preference in respect of
dividends or of amounts payable in the event of any voluntary or involuntary
liquidation, dissolution or winding up of the Company and which are not subject
to redemption by the Company; PROVIDED that if at any time there shall be more
than one such resulting class, the shares of each such class then so issuable
pursuant to the terms hereof shall be substantially in the proportion which the
total number of shares of such class

<PAGE>   8
resulting from all such reclassifications bears to the total number of shares of
all such classes resulting from all such reclassifications.

         "COMPANY" means the party named as the "Company" in the first paragraph
of this Indenture until a successor replaces it pursuant to the applicable
provisions of this Indenture and, thereafter, shall mean such successor. The
foregoing sentence shall likewise apply to any subsequent such successor or
successors.

         "COMPANY REQUEST" or "COMPANY ORDER" means a written request or order
signed in the name of the Company by its Chairman of the Board, a Vice Chairman,
its President or a Vice President, and by its Treasurer, an Assistant Treasurer,
its Controller, an Assistant Controller, its Corporate Secretary or an Assistant
Corporate Secretary, and delivered to the Trustee.

         "CORPORATE TRUST OFFICE" means the principal office of the Trustee at
which at any particular time its corporate trust business shall be principally
administered, which office is, at the date as of which this Indenture is dated,
located at 100 East Broad Street, 8th Floor, Columbus, Ohio 43215, Attention:
Global Corporate Trust Services.

         "CUSTODIAN" shall mean the Trustee, as custodian with respect to the
Securities in global form, or any successor entity thereto.

         "DEFAULT" means any event which is, or after notice or passage of time
or both would be, an Event of Default.

         "DEPOSITARY" means, with respect to the Securities issuable or issued
in whole or in part in global form, the Person specified in Section 2.06 as the
Depositary with respect to the Securities, until a successor shall have been
appointed and become such pursuant to the applicable provisions of this
Indenture, and thereafter, "Depositary" shall mean or include such successor.

         "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended,
and the rules and regulations of the SEC promulgated thereunder.

         "FUNDAMENTAL CHANGE" means the occurrence of any transaction or event
in connection with which all or substantially all Common Stock shall be
exchanged for, converted into, acquired for or constitute solely the right to
receive (whether by means of an exchange offer, liquidation, tender offer,
consolidation, merger, combination, reclassification, recapitalization or
otherwise) consideration which is not all or substantially all common stock
listed (or, upon consummation of or immediately following such transaction or
event, which will be listed) on a United States national securities exchange or
approved for quotation on The NASDAQ National Market or any similar United
States system of automated dissemination of quotations of securities prices.

         "HOLDER" means a Person in whose name a Security is registered on the
Registrar's books.

                                       2
<PAGE>   9

         "INDENTURE" means this Indenture, as amended or supplemented from time
to time in accordance with the terms hereof.

         "INITIAL PURCHASER" means Morgan Stanley & Co. Incorporated.

         "ISSUE DATE" of any Security means February 5, 2001.

         "ISSUE PRICE" of any Security means, in connection with the original
issuance of such Security, the initial issue price at which the Security is
issued as set forth on the face of the Security.

         "LEGAL HOLIDAY" is any day other than a Business Day. If any specified
date (including a date for giving notice) is a Legal Holiday, the action shall
be taken on the next succeeding date that is not a Legal Holiday, and to the
extent applicable no Original Issue Discount or interest, if any, shall accrue
for the intervening period.

         "MARKET PRICE" means, as of any Repurchase Date or date of
determination, the average of the Sale Prices of the Common Stock for the five
Trading Day period ending on the third Business Day prior to the applicable
Repurchase Date or date of determination (if the third Business Day prior to the
applicable Repurchase Date or date of determination is a Trading Day or, if it
is not a Trading Day, then on the last Trading Day prior to such third Business
Day), appropriately adjusted to take into account the occurrence, during the
period commencing on the first of such Trading Days during such five Trading Day
period and ending on such Repurchase Date or date of determination, of any event
described in Sections 11.06, 11.07 or 11.08 hereof; subject, however, to the
conditions set forth in Sections 11.09 and 11.10 hereof.

         "NASDAQ NATIONAL MARKET" means the electronic inter-dealer quotation
system operated by NASDAQ Stock Market, Inc., a subsidiary of the National
Association of Securities Dealers, Inc.

         "NON-U.S. PERSON" means a Person that is not a U.S. Person.

         "OFFICER" means the Chairman of the Board, any Vice Chairman, the
President, any Vice President, the Treasurer or the Secretary or any Assistant
Treasurer or Assistant Secretary of the Company.

         "OFFICERS' CERTIFICATE" means a written certificate containing the
information specified in Sections 13.04 and 13.05, signed in the name of the
Company by its Chairman of the Board, a Vice Chairman, its President or a Vice
President, and by its Treasurer, an Assistant Treasurer, its Controller, an
Assistant Controller, its Corporate Secretary or an Assistant Corporate
Secretary, and delivered to the Trustee.

         "OPINION OF COUNSEL" means a written opinion containing the information
specified in Sections 13.04 and 13.05, from legal counsel who is acceptable to
the Trustee. The counsel may be an employee of, or counsel to, the Company or
the Trustee.

                                       3
<PAGE>   10

         "ORIGINAL ISSUE DISCOUNT" of any Security means the difference between
the Principal Amount and the Issue Price of the Security as set forth on the
face of the Security. For purposes of this Indenture and the Securities, accrual
of Original Issue Discount shall be calculated on the basis of a 360-day year of
twelve 30-day months.

         "PERSON" means any individual, corporation, partnership, limited
liability company, joint venture, association, joint-stock company, trust,
unincorporated organization, or government or any agency or political
subdivision thereof.

         "PRINCIPAL" or "PRINCIPAL AMOUNT" of a Security means the principal
amount at Stated Maturity as set forth on the face of such Security, or on
Schedule A thereto in the case of a Security in global form.

         "QIB" means "qualified institutional buyer" as that term is defined in
Rule 144A.

         "REDEMPTION DATE" means a date specified for redemption of the
Securities in accordance with the terms of the Securities and Section 3.01 of
this Indenture.

         "REDEMPTION PRICE" shall have the meaning set forth in paragraph 5 of
the Securities.

         "REGISTRATION RIGHTS AGREEMENT" means the Registration Rights Agreement
dated as of January 31, 2001 between the Company and the Initial Purchaser.

         "REGULATION S" means Regulation S as promulgated under the Securities
Act.

         "RULE 144" means Rule 144 as promulgated under the Securities Act.

         "RULE 144A means Rule 144A as promulgated under the Securities Act.

         "SALE PRICE OF THE COMMON STOCK" means, on any date, the closing per
share sale price, or if no closing sale price is reported, the average bid and
ask prices or, if more than one, in either case, the average of the average bid
and average ask prices, on such date as reported in the composite transactions
for the principal United States securities exchange on which the Common Stock is
traded or, if the common stock is not listed on a United States national or
regional stock exchange, as reported by The NASDAQ National Market.

         "SEC" or "COMMISSION" means the Securities and Exchange Commission or
any successor entity.

         "SECURITIES" means the Company's Zero Coupon Convertible Senior
Debentures due 2021; PROVIDED, HOWEVER, that if the Company exercises the option
provided for in Section 12.01 hereof, on and after the Option Exercise Date all
references herein to Securities shall be deemed to mean the Semiannual Coupon
Debentures, unless the context otherwise indicates.

                                       4
<PAGE>   11

         "SECURITIES ACT" means the Securities Act of 1933, as amended, and the
rules and regulations of the SEC promulgated thereunder.

         "STATED MATURITY," when used with respect to any Security, means the
date specified in such Security as the fixed date on which an amount equal to
the Principal of such Security is due and payable.

         "TAX EVENT" means that the Company has received an opinion from
independent tax counsel experienced in such matters to the effect that, as a
result of: (1) an amendment to, or change or announced prospective change in,
the laws or regulations of the U.S. or any political subdivision or taxing
authority thereof or therein; or (2) any amendment to, or change in, an
interpretation or application of such laws or regulations by any legislative
body, court, governmental agency or regulatory authority, in each case which
amendment or change is enacted, promulgated, issued or announced or which
interpretation is issued or announced or which action is taken, on or after
January 31, 2001, there is more than an insubstantial risk that interest,
including original issue discount, payable on the Securities either (a) would
not be deductible on a current accrual basis or (b) would not be deductible
under any other method, in either case in whole or in part, by the Company by
reason of deferral, disallowance or otherwise for U.S. federal income tax
purposes.

         "TIA" means the Trust Indenture Act of 1939, as amended, as in effect
on the date of this Indenture, except as provided in Section 9.03.

         "TRADING DAY" means a day during which trading in securities generally
occurs on the AMEX or, if the applicable security is not listed on the AMEX, on
the NASDAQ National Market, or if the applicable security is not quoted on the
NASDAQ National Market, on the principal other national or regional securities
exchange on which the applicable security is then listed or, if the applicable
security is not listed on a national or regional securities exchange, on the
principal other market on which the applicable security is then traded.

         "TRUST OFFICER" means any officer within the corporate trust department
of the Trustee, including any vice president, assistant vice president,
assistance secretary, assistant treasurer, trust officer or any other officer of
the Trustee who customarily performs functions similar to those performed by the
Persons who at the time shall be such officers, respectively, or to whom any
corporate trust matter is referred because of such person's knowledge of and
familiarity with the particular subject and who shall have direct responsibility
for the administration of this Indenture.

         "TRUSTEE" means the party named as the "Trustee" in the first paragraph
of this Indenture until a successor replaces it pursuant to the applicable
provisions of this Indenture and, thereafter, shall mean such successor. The
foregoing sentence shall likewise apply to any subsequent such successor or
successors.

         "U.S. PERSON" has the meaning specified in Regulation S.

                                       5
<PAGE>   12

         "VOTING STOCK" means stock of any class or classes, however designated,
having ordinary voting power for the election of a majority of the board of
directors of a corporation, other than stock having such power only by reason of
the occurrence of a contingency.

         SECTION 1.02.     OTHER DEFINITIONS.

<TABLE>
<CAPTION>
                                                                                              DEFINED
TERM                                                                                        IN SECTION
----                                                                                        ----------

<S>                                                                                          <C>
"CASH"......................................................................................  3.08(b)
"CLEARSTREAM"...............................................................................  2.06(c)
"COMPANY NOTICE"............................................................................  3.08(e)
"COMPANY NOTICE DATE".......................................................................  3.08(c)
"CONVERSION AGENT"..........................................................................  2.03
"CONVERSION DATE"........................................................................... 11.02
"CONVERSION RATE"........................................................................... 11.01
"DEFAULTED INTEREST"........................................................................ 12.02(b)
"DISTRIBUTED SECURITIES".................................................................... 11.08(a)
"EUROCLEAR".................................................................................  2.06(c)
"EVENT OF DEFAULT"..........................................................................  6.01
"FUNDAMENTAL CHANGE PURCHASE PRICE".........................................................  3.09(a)
"FUNDAMENTAL CHANGE REPURCHASE DATE"........................................................  3.09(a)
"FUNDAMENTAL CHANGE REPURCHASE NOTICE"......................................................  3.09(b)
"INTEREST PAYMENT DATE"..................................................................... 12.01
"LIQUIDATED DAMAGES"........................................................................  4.08(a)
"NOTICE OF DEFAULT".........................................................................  6.01
"OPTION"....................................................................................  2.02
"OPTION EXERCISE DATE"...................................................................... 12.01
"PAYING AGENT"..............................................................................  2.03
"PURCHASE PRICE"............................................................................  3.08(a)
"REGISTRAR".................................................................................  2.03
"REGULAR RECORD DATE"....................................................................... 12.01
"REPURCHASE DATE"...........................................................................  3.08(a)
"REPURCHASE NOTICE".........................................................................  3.08(a)
"RESTATED PRINCIPAL AMOUNT"................................................................. 12.01
"RESTRICTED SECURITIES".....................................................................  2.06(c)
"RESTRICTED SECURITY LEGEND"................................................................  2.06(c)
"SEMIANNUAL COUPON DEBENTURE"............................................................... 12.01
"SHELF REGISTRATION STATEMENT"..............................................................  4.08(a)
"SPECIAL RECORD DATE"....................................................................... 12.02(a)
"TAX EVENT DATE"............................................................................ 12.01
"TRIGGER EVENT"............................................................................. 11.19
</TABLE>

                                       6
<PAGE>   13

         SECTION 1.03. INCORPORATION BY REFERENCE OF TRUST INDENTURE ACT.

         Whenever this Indenture refers to a provision of the TIA, the provision
is incorporated by reference in and made a part of this Indenture. The following
TIA terms used in this Indenture have the following meanings:

         "Commission" means the SEC.

         "Indenture Securities" means the Securities.

         "Indenture Security Holder" means a Holder.

         "Indenture to be Qualified" means this Indenture.

         "Indenture Trustee" or "Institutional Trustee" means the Trustee.

         All other TIA terms used in this Indenture that are defined by the TIA,
defined by TIA reference to another statute or defined by SEC rules have the
meanings assigned to them by such definitions.

         SECTION 1.04. RULES OF CONSTRUCTION.

         Unless the context otherwise requires:

                  (1)      a term has the meaning assigned to it;

                  (2)      an accounting term not otherwise defined has the
meaning assigned to it in accordance with generally accepted accounting
principles in the United States of America as in effect from time to time;

                  (3)      "or" is not exclusive;

                  (4)      "including" means including, without limitation;

                  (5)      the term "merger" includes a statutory compulsory
share exchange and a conversion of a corporation into a limited liability
company, a partnership or other entity and vice versa;

                  (6)      references to statutes, rules or regulations include
any successor statute, rule or regulation, as the case may be;

                  (7)      the masculine gender includes the feminine and the
neuter; and

                  (8)      words in the singular include the plural, and words
in the plural include the singular.

                                       7
<PAGE>   14

                                   ARTICLE 2.
                                 THE SECURITIES

         SECTION 2.01.     FORM AND DATING.

         Other than as provided in Section 2.06, the Securities and the
Trustee's certificate of authentication for the Securities shall be
substantially in the form of EXHIBIT A, which is a part of this Indenture. In
addition to such legends as may be required by Section 2.06, the Securities may
have notations, legends or endorsements required by law, stock exchange rule or
usage, PROVIDED that any such notation, legend or endorsement required by usage
is in a form acceptable to the Company. The Company shall provide any such
notations, legends or endorsements to the Trustee in writing. Each Security
shall be dated the date of its authentication.

         Any Security in global form shall represent such of the outstanding
Securities as shall be specified therein and shall provide that it shall
represent the aggregate amount of outstanding Securities from time to time
endorsed thereon and that the aggregate amount of outstanding Securities
represented thereby may from time to time be increased or reduced to reflect
transfers or exchanges permitted hereby. Any endorsement of a Security in global
form to reflect the amount of any increase or decrease in the amount of
outstanding Security represented thereby shall be made by the Trustee or the
Custodian, at the direction of the Trustee, in such manner and upon instructions
given by the Holder of such Security in accordance with this Indenture. Payment
of Principal Amount, Issue Price, accrued Original Issue Discount, Redemption
Price, Purchase Price, Fundamental Change Purchase Price, Liquidated Damages, if
any, or interest, if any, on any Security in global form shall be made to the
Holder of such Security.

         SECTION 2.02.     EXECUTION AND AUTHENTICATION.

         The Securities shall be executed on behalf of the Company by its
Chairman of the Board, one of its Vice Chairmen, its President or one of its
Vice Presidents. The signature of any of these officers on the Securities may be
manual or facsimile.

         Securities bearing the manual or facsimile signatures of individuals
who were at any time the proper Officers of the Company shall bind the Company,
notwithstanding that such individuals or any of them have ceased to hold such
offices prior to the authentication and delivery of such Securities or did not
hold such offices at the date of authentication of such Securities.

         No Security shall be entitled to any benefit under this Indenture or be
valid or obligatory for any purpose unless there appears on such Security a
certificate of authentication substantially in the form provided for herein duly
executed by the Trustee by manual signature of an authorized signatory, and such
certificate upon any Security shall be conclusive evidence, and the only
evidence, that such Security has been duly authenticated and delivered
hereunder.

                                       8
<PAGE>   15

         The Trustee shall authenticate and deliver Securities for original
issue in an aggregate Principal Amount of $1,151,000,000 upon a Company Order
without any further action by the Company (or an aggregate Principal Amount not
to exceed $1,381,200,000 if the option ("OPTION") set forth in Section 2 of the
Purchase Agreement dated January 31, 2001 (as amended from time to time by the
parties thereto) by and between the Company and the Initial Purchaser is
exercised in full). The aggregate Principal Amount of Securities outstanding at
any time may not exceed the amount set forth in the foregoing sentence, except
as provided in Section 2.07 hereof.

         SECTION 2.03.     REGISTRAR, PAYING AGENT AND CONVERSION AGENT.

         The Company shall maintain an office or agency where Securities may be
presented for registration of transfer or for exchange ("REGISTRAR"), an office
or agency where Securities may be presented for purchase or payment ("PAYING
AGENT") and an office or agency where Securities may be presented for conversion
into Common Stock ("CONVERSION AGENT"). The Registrar shall keep a register of
the Securities and of their transfer and exchange. The Company may have one or
more co-registrars, one or more additional paying agents and one or more
additional conversion agents. The term Paying Agent includes any additional
paying agent. The term Conversion Agent includes any additional conversion
agent, including any named in accordance with the provisions hereof.

         The Company shall enter into an appropriate agency agreement with any
Registrar, Paying Agent, Conversion Agent or co-registrar (if not the Trustee or
an Affiliate of the Trustee). The agreement shall implement the provisions of
this Indenture that relate to such agent and the relevant Security. The Company
shall notify the Trustee of the name and address of any such agent. If the
Company fails to maintain a Registrar, Paying Agent or Conversion Agent, the
Trustee shall act as such and shall be entitled to appropriate compensation
therefor pursuant to Section 7.07 hereof. The Company or an Affiliate of the
Company may act as Paying Agent, Registrar, Conversion Agent or co-registrar.

         The Company initially appoints the Trustee as Registrar, Conversion
Agent and Paying Agent in connection with the Securities.

         SECTION 2.04.     PAYING AGENT TO HOLD CASH AND SECURITIES IN TRUST.

         Except as otherwise provided herein, prior to or on each due date of
payments in respect of any Security, the Company shall deposit with the Paying
Agent cash or securities sufficient to make such payments when such payments are
due. The Company shall require the Paying Agent (if not the Trustee) to agree in
writing that the Paying Agent shall hold in trust for the benefit of Holders or
the Trustee all cash and securities held by the Paying Agent for the making of
payments in respect of the Securities and shall notify the Trustee of any
default by the Company in making any such payment. At any time during the
continuance of any such default, the Paying Agent shall, upon the written
request of the Trustee, forthwith pay to the Trustee all cash and securities so
held in trust. If the Company or an Affiliate of the Company acts as Paying
Agent, it shall segregate the cash and securities held by it as Paying Agent and
hold it as a

                                       9
<PAGE>   16
 separate trust fund. The Company at any time may require the Paying Agent to
pay all cash and securities held by it to the Trustee and to account for any
funds and securities disbursed by it. Upon doing so, the Paying Agent shall have
no further liability for such cash or securities.

         SECTION 2.05.     HOLDER LISTS.

         The Trustee shall preserve in as current a form as is reasonably
practicable the most recent list available to it of the names and addresses of
Holders. If the Trustee is not the Registrar, the Company shall cause to be
furnished to the Trustee at least semiannually on January 26 and July 26 a
listing of Holders dated within ten days of the date on which the list is
furnished and at such other times as the Trustee may request in writing a list,
in such form and as of such date as the Trustee may reasonably require, of the
names and addresses of Holders.

         SECTION 2.06.     EXCHANGE AND REGISTRATION OF TRANSFER OF SECURITIES;
RESTRICTIONS ON TRANSFERS; DEPOSITARY.

                  (a) Upon surrender for registration of transfer of any
Security at any office or agency of the Company designated as Registrar or
co-registrar pursuant to Section 2.03 hereof and satisfaction of the
requirements for such transfer set forth in this Section 2.06, the Company shall
execute, and the Trustee shall authenticate and deliver, in the name of the
designated transferee or transferees, one or more new Securities of any
authorized denominations and of a like aggregate Principal Amount and bearing
such restrictive legends as may be required by this Indenture.

         Securities may be exchanged for a like aggregate Principal Amount of
Securities of other authorized denominations. Securities to be exchanged shall
be surrendered at any office or agency to be maintained by the Company
designated as Registrar or co-registrar pursuant to Section 2.03 hereof and the
Company shall execute and register, and the Trustee shall authenticate and
deliver in exchange therefor, the Security or Securities which the Holder making
the exchange shall be entitled to receive, bearing registration numbers not
contemporaneously outstanding.

         All Securities presented for registration of transfer or for exchange
into like Securities, repurchase, redemption or conversion into Common Stock or
payment shall (if so required by the Company, the Trustee, the Registrar or any
co-registrar) be duly endorsed by, or be accompanied by a written instrument or
instruments of transfer in form satisfactory to the Company and the Trustee,
duly executed by the Holder or such Holder's attorney duly authorized in
writing.

         No service charge shall be charged to the Holder for any exchange for
like Securities or registration of transfer of Securities, but the Company may
require payment of a sum sufficient to cover any tax, assessments or other
governmental charges that may be imposed in connection therewith.

         None of the Company, the Trustee, the Registrar or any co-registrar
shall be required to exchange for like Securities or register a transfer of (a)
any Securities for a period of 15 days next preceding the mailing of notice of
Securities to be redeemed, or (b) any Securities or

                                       10
<PAGE>   17

portions thereof selected or called for redemption, or (c) any Securities or
portion thereof surrendered for conversion into Common Stock, or (d) any
Securities or portion thereof surrendered for repurchase or redemption (and not
withdrawn) pursuant to Section 3.08 or 3.09 hereof, respectively.

         All Securities issued upon any transfer or exchange for like Securities
shall be valid obligations of the Company, evidencing the same debt, and
entitled to the same benefits under this Indenture as the Securities surrendered
upon such exchange or transfer.

                  (b) So long as the Securities are eligible for book-entry
settlement with the Depositary, or unless otherwise required by law, all
Securities that are so eligible may be represented by a Security in global form
registered in the name of the Depositary or the nominee of the Depositary,
except as otherwise specified below. The transfer and exchange of beneficial
interests in such Security in global form shall be effected through the
Depositary in accordance with this Indenture and the procedures of the
Depositary therefor.

         Any Security in global form may be endorsed with or have incorporated
in the text thereof such legends or recitals or changes not inconsistent with
the provisions of this Indenture as may be required by the Custodian, the
Depositary or by the National Association of Securities Dealers, Inc. in order
for the Securities to be tradeable on any market developed for trading of
securities pursuant to Rule 144A or Regulation S or required to comply with any
applicable law or any regulation thereunder or with the rules and regulations of
any securities exchange or automated quotation system upon which the Securities
may be listed or traded or to conform with any usage with respect thereto, or to
indicate any special limitations or restrictions to which any particular
Securities are subject.

                  (c) Every Security that bears or is required under this
Section 2.06(c) to bear the Restricted Securities Legend (together with any
Common Stock issued upon conversion of the Securities and required to bear the
legend set forth in Section 2.06(d), collectively, the "RESTRICTED SECURITIES")
shall be subject to the restrictions on transfer set forth in this Section
2.06(c) (including those set forth in the legend set forth below) unless such
restrictions on transfer shall be waived by written consent of the Company, and
the Holder of each such Transfer Restricted Security, by such Holder's
acceptance thereof, agrees to be bound by all such restrictions on transfer. As
used in Section 2.06(c) and 2.06(d), the term "transfer" encompasses any sale,
pledge, transfer or other disposition whatsoever of any Restricted Security.

         Until transferred under Rule 144(k) under the Securities Act (or any
successor provision), any certificate evidencing such Security (and all
securities issued in exchange therefor or substitution thereof, other than
Common Stock issued upon conversion or repurchase thereof, which shall bear the
legend set forth in Section 2.06(d) if applicable) shall bear a legend in
substantially the form set forth on the face of the Security in EXHIBIT A (the
"RESTRICTED SECURITY LEGEND"), unless such Security has been sold pursuant to a
registration statement that has been declared effective under the Securities Act
(and which continues to be effective at the time of such transfer), or unless
otherwise agreed by the Company in writing, with written notice thereof to the
Trustee.

                                       11
<PAGE>   18

         Any Security (or security issued in exchange or substitution therefor)
as to which the conditions for removal of the Restricted Security Legend have
been satisfied may, upon surrender of such Security for exchange to the
Registrar in accordance with the provisions of this Section 2.06, be exchanged
for a new Security or Securities, of like tenor and aggregate Principal Amount,
which shall not bear the Restricted Security Legend required by this Section
2.06(c).

         Notwithstanding any other provisions of this Indenture (other than the
provisions set forth in Section 2.06(b) and in this Section 2.06(c)), a Security
in global form may not be transferred as a whole or in part except by the
Depositary to a nominee of the Depositary or by a nominee of the Depositary to
the Depositary or another nominee of the Depositary or by the Depositary or any
such nominee to a successor Depositary or a nominee of such successor
Depositary.

         The Depositary shall be a clearing agency registered under the Exchange
Act. The Company initially appoints The Depository Trust Company to act as
Depositary. Initially, one or more Securities in global form shall be issued to
the Depositary, registered in the name of Cede & Co., as the nominee of the
Depositary, and deposited with the Custodian for Cede & Co. Each Security in
global form, to the extent that it represents the interests of Non-U.S. Persons,
will be held by Cede & Co. for the accounts of designated agents on behalf of
the Euroclear System ("Euroclear") and Clearstream Banking, Societe Anonyme
("Clearstream"). During the 40-day distribution compliance period (as defined in
Regulation S), Non-U.S. Persons holding beneficial interests in a Security in
global form may do so only through Euroclear or Clearstream, and any resale or
transfer of any such interest to a U.S. Person shall only be permitted if such
Person is a QIB or is the Company or an Affiliate of the Company.

         If at any time the Depositary for Security in global form notifies the
Company that it is unwilling or unable to continue as Depositary for such
Security, the Company may appoint a successor Depositary with respect to such
Security. If a successor Depositary is not appointed by the Company within
ninety (90) days after the Company receives such notice, the Company will
execute, and the Trustee, upon receipt of an Officers' Certificate for the
authentication and delivery of Securities, will authenticate and deliver,
Securities in certificated or definitive form, in aggregate Principal Amount
equal to the Principal Amount of the Security in global form, in exchange for
such Security in global form.

         Securities in certificated form issued in exchange for all or a part of
a Security in global form pursuant to this Section 2.06 shall be registered in
such names and in such authorized denominations as the Depositary, pursuant to
instructions from its direct or indirect participants or otherwise, shall
instruct the Trustee. Upon execution and authentication, the Trustee shall
deliver such Securities in certificated form to the persons in whose names such
Securities in certificated form are so registered.

         At such time as all interests in a Security in global form have been
redeemed, converted, canceled or repurchased or exchanged for Securities in
certificated form, or transferred to a transferee who receives Securities in
certificated form, such Security in global form shall, upon receipt thereof, be
canceled by the Trustee in accordance with standing procedures and instructions
existing between the Depositary and the Custodian. At any time prior to such
cancellation, if any interest in a Security in global form is exchanged for
Securities in certificated

                                       12
<PAGE>   19

form, redeemed, converted, repurchased or canceled, the Principal Amount of the
Security in global form shall, in accordance with the standing procedures and
instructions existing between the Depositary and the Custodian, be appropriately
reduced and an endorsement shall be made on such Security in global form, by the
Trustee or the Custodian, at the direction of the Trustee, to reflect such
reduction.

                  (d) Until transferred under Rule 144(k) under the Securities
Act (or any successor provision), any stock certificate representing Common
Stock issued upon conversion or repurchase of any Security shall bear a legend
in substantially the following form, unless such Common Stock has been sold
pursuant to a registration statement that has been declared effective under the
Securities Act (and which continues to be effective at the time of such
transfer) or such Common Stock has been issued upon conversion or repurchase of
Securities that have been transferred pursuant to a registration statement that
has been declared effective under the Securities Act, or unless otherwise agreed
by the Company in writing with written notice thereof to the transfer agent for
the Common Stock:

         THE COMMON STOCK EVIDENCED HEREBY HAS NOT BEEN REGISTERED UNDER THE
         UNITED STATES SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES
         ACT"), OR ANY STATE SECURITIES LAWS, AND, ACCORDINGLY, MAY NOT BE
         OFFERED OR SOLD WITHIN THE UNITED STATES OR TO, OR FOR THE ACCOUNT OR
         BENEFIT OF, UNITED STATES PERSONS EXCEPT AS SET FORTH IN THE FOLLOWING
         SENTENCE. THE HOLDER HEREOF AGREES THAT UNTIL THE EXPIRATION OF THE
         HOLDING PERIOD APPLICABLE TO SALES OF THE SECURITY EVIDENCED HEREBY
         UNDER RULE 144(k) UNDER THE SECURITIES ACT (OR ANY SUCCESSOR
         PROVISION), (1) IT WILL NOT RESELL OR OTHERWISE TRANSFER THE COMMON
         STOCK EVIDENCED HEREBY WITHIN THE UNITED STATES OR TO, OR FOR THE
         ACCOUNT OF, UNITED STATES PERSONS EXCEPT (A) TO NABORS INDUSTRIES, INC.
         OR ANY SUBSIDIARY THEREOF, (B) TO A "QUALIFIED INSTITUTIONAL BUYER" (AS
         DEFINED IN RULE 144A UNDER THE SECURITIES ACT), (C) TO AN INSTITUTIONAL
         "ACCREDITED INVESTOR" (AS DEFINED IN RULE 501(a)(1), (2), (3) OR (7)
         UNDER THE SECURITIES ACT) THAT PRIOR TO SUCH TRANSFER, FURNISHES TO
         FIRST CHICAGO TRUST COMPANY OF NEW YORK, AS TRANSFER AGENT (OR A
         SUCCESSOR TRANSFER AGENT, AS APPLICABLE), A SIGNED LETTER CONTAINING
         CERTAIN REPRESENTATIONS AND AGREEMENTS RELATING TO THE RESTRICTIONS ON
         TRANSFER OF THE COMMON STOCK EVIDENCED HEREBY (THE FORM OF WHICH LETTER
         CAN BE OBTAINED FROM SUCH TRANSFER AGENT OR A SUCCESSOR TRANSFER AGENT,
         AS APPLICABLE), (D) PURSUANT TO THE EXEMPTION FROM REGISTRATION
         PROVIDED BY RULE 144 UNDER THE SECURITIES ACT (IF AVAILABLE) OR (E)
         PURSUANT TO A REGISTRATION STATEMENT WHICH HAS BEEN DECLARED EFFECTIVE
         UNDER THE SECURITIES ACT (AND WHICH CONTINUES TO BE EFFECTIVE AT THE
         TIME OF

                                       13
<PAGE>   20

         SUCH TRANSFER); (2) PRIOR TO SUCH TRANSFER (OTHER THAN A TRANSFER
         PURSUANT TO CLAUSE 1(E) ABOVE), IT WILL FURNISH TO FIRST CHICAGO TRUST
         COMPANY OF NEW YORK, AS TRANSFER AGENT (OR A SUCCESSOR TRANSFER AGENT,
         AS APPLICABLE), SUCH CERTIFICATIONS, LEGAL OPINIONS OR OTHER
         INFORMATION AS THE TRANSFER AGENT MAY REASONABLY REQUIRE TO CONFIRM
         THAT SUCH TRANSFER IS BEING MADE PURSUANT TO AN EXEMPTION FROM, OR IN A
         TRANSACTION NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE
         SECURITIES ACT AND (3) IT WILL DELIVER TO EACH PERSON TO WHOM THE
         COMMON STOCK EVIDENCED HEREBY IS TRANSFERRED (OTHER THAN A TRANSFER
         PURSUANT TO CLAUSE 1(E) ABOVE) A NOTICE SUBSTANTIALLY TO THE EFFECT OF
         THIS LEGEND. THIS LEGEND WILL BE REMOVED UPON THE EARLIER OF THE
         TRANSFER OF THE COMMON STOCK EVIDENCED HEREBY PURSUANT TO CLAUSE 1(E)
         ABOVE OR UPON ANY TRANSFER OF THE COMMON STOCK EVIDENCED HEREBY AFTER
         THE EXPIRATION OF THE HOLDING PERIOD APPLICABLE TO SALES OF THE
         SECURITIES EVIDENCED HEREBY UNDER RULE 144(k) UNDER THE SECURITIES ACT
         (OR ANY SUCCESSOR PROVISION). AS USED HEREIN, THE TERMS "UNITED STATES"
         AND "UNITED STATES PERSON" HAVE THE MEANING GIVEN TO THEM BY REGULATION
         S UNDER THE SECURITIES ACT.

         Any such Common Stock as to which such restrictions on transfer shall
have expired in accordance with their terms or as to which the conditions for
removal of the foregoing legend set forth therein have been satisfied may, upon
surrender of the certificates representing such shares of Common Stock for
exchange in accordance with the procedures of the transfer agent for the Common
Stock, be exchanged for a new certificate or certificates for a like number of
shares of Common Stock, which shall not bear the restrictive legend required by
this Section 2.06(d).

                  (e) Any Security that, prior to the expiration of the holding
period applicable to sales thereof under Rule 144(k) under the Securities Act,
is purchased or owned by the Company or any Affiliate thereof may not be resold
by the Company or such Affiliate unless registered under the Securities Act or
resold pursuant to an exemption from the registration requirements of the
Securities Act in a transaction which results in such Security no longer being
"restricted securities" (as defined under Rule 144).

                  (f) Each Holder of a Security agrees to indemnify the Company
and the Trustee against any liability that may result from the transfer,
exchange or assignment of such Holder's Security in violation of any provision
of this Indenture and/or applicable United States Federal or state securities
law or foreign securities laws.

         The Trustee shall have no obligation or duty to monitor, determine or
inquire as to compliance with any restrictions on transfer imposed under this
Indenture or under applicable law with respect to any transfer of any interest
in any Security (including any transfers between or among Depositary
participants or beneficial owners of interests in a Security in global form)

                                       14
<PAGE>   21

other than to require delivery of such certificates and other documentation or
evidence as are expressly required by, and to do so if and when expressly
required by the terms of, this Indenture, and to examine the same to determine
substantial compliance as to form with the express requirements hereof.

         SECTION 2.07.     REPLACEMENT SECURITIES.

         If (a) any mutilated Security is surrendered to the Trustee, or (b) the
Company and the Trustee receive evidence to their satisfaction of the
destruction, loss or theft of any Security, and there is delivered to the
Company and the Trustee such security or indemnity as may be required by them to
save each of them harmless, then, in the absence of notice to the Company or the
Trustee that such Security has been acquired by a bona fide purchaser, the
Company shall execute and, upon its written request, the Trustee shall
authenticate and deliver, in exchange for any such mutilated Security or in lieu
of any such destroyed, lost or stolen Security, a new Security of like tenor and
Principal Amount, bearing a number not contemporaneously outstanding.

         In case any such mutilated, destroyed, lost or stolen Security has
become or is about to become due and payable, or is about to be repurchased or
redeemed by the Company pursuant to Article 3 hereof, or converted pursuant to
Article 11 hereof, the Company in its discretion may, instead of issuing a new
Security, pay, repurchase or redeem such Security, or issue the underlying
securities, as the case may be.

         Upon the issuance of any new Securities under this Section 2.07, the
Company may, as a condition to such issuance, require the payment of a sum
sufficient to cover any tax or other governmental charge that may be imposed in
relation thereto and any other expenses (including the fees and expenses of the
Trustee) connected therewith.

         Every new Security issued pursuant to this Section 2.07 in lieu of any
mutilated, destroyed, lost or stolen Security shall constitute an original
additional contractual obligation of the Company, whether or not the mutilated
destroyed, lost or stolen Security shall be at any time enforceable by anyone,
and shall be entitled to all benefits of this Indenture equally and
proportionately with any and all other Securities duly issued hereunder.

         The provisions of this Section 2.07 are exclusive and shall preclude
(to the extent lawful) all other rights and remedies with respect to the
replacement or payment of mutilated, destroyed, lost or stolen Securities.

         SECTION 2.08.     OUTSTANDING SECURITIES; DETERMINATIONS OF HOLDERS'
ACTION.

         Securities outstanding at any time are all the Securities authenticated
by the Trustee except for those canceled by it, those delivered to it for
cancellation, those paid pursuant to Section 4.01 hereof, those replaced or paid
pursuant to Section 2.07 hereof and those described in this Section 2.08 as not
outstanding. A Security does not cease to be outstanding because the Company or
an Affiliate thereof holds the Security; PROVIDED, HOWEVER, that in

                                       15
<PAGE>   22

determining whether the Holders of the requisite Principal Amount of Securities
have given or concurred in any request, demand, authorization, direction,
notice, consent or waiver hereunder, Securities owned by the Company or any
Affiliate of the Company shall be disregarded and deemed not to be outstanding,
except that, in determining whether the Trustee shall be protected in relying
upon any such request, demand, authorization, direction, notice, consent or
waiver, only Securities which the Trust Officer actually knows to be so owned
shall be so disregarded unless written notice of such ownership is received by
the Trustee at the Corporate Trust Office of the Trustee in accordance with
Section 13.02 hereof and such notice references the Securities and this
Indenture. Subject to the foregoing, only Securities outstanding at the time of
such determination shall be considered in any such determination (including
determinations pursuant to Articles 6 and 9 hereof).

         If a Security is replaced pursuant to Section 2.07, it ceases to be
outstanding unless the Trustee receives proof satisfactory to it that the
replaced Security is held by a bona fide purchaser.

         If the Paying Agent holds, in accordance with this Indenture, on a
Redemption Date, or on the Business Day following a Repurchase Date or a
Fundamental Change Repurchase Date, or on Stated Maturity, cash or securities,
if permitted hereunder, sufficient to pay Securities payable on that date, then
on and after that date such Securities shall cease to be outstanding and
Original Issue Discount, Liquidated Damages, if any, and interest, if any, on
such Securities shall cease to accrue; PROVIDED, that, if such Securities are to
be redeemed or repurchased, notice of such redemption or repurchase has been
duly given pursuant to this Indenture or provision therefor satisfactory to the
Trustee has been made.

         If a Security is converted in accordance with Article 11 hereof, then
from and after such conversion such Security shall cease to be outstanding and
Original Issue Discount and interest, if any, shall cease to accrue on such
Security.

         SECTION 2.09.     TEMPORARY SECURITIES.

         Pending the preparation of definitive Securities, the Company may
execute, and upon Company Order the Trustee shall authenticate and deliver,
temporary Securities which are printed, lithographed, typewritten, mimeographed
or otherwise produced, in any authorized denomination, substantially of the
tenor of the definitive Securities in lieu of which they are issued and with
such appropriate insertions, omissions, substitutions and other variations as
the officers executing such Securities may determine, as conclusively evidenced
by their execution of such Securities.

         If temporary Securities are issued, the Company shall cause definitive
Securities to be prepared without unreasonable delay. After the preparation of
definitive Securities, the temporary Securities shall be exchangeable for
definitive Securities upon surrender of the temporary Securities at the office
or agency of the Company designated for such purpose pursuant to Section 2.03
hereof, without charge to the Holder. Upon surrender for cancellation of any one
or more temporary Securities, the Company shall execute and the Trustee shall
authenticate and deliver in exchange therefor a like Principal Amount of
definitive Securities of

                                       16
<PAGE>   23

authorized denominations. Until so exchanged, the temporary Securities shall in
all respects be entitled to the same benefits under this Indenture as definitive
Securities.

         SECTION 2.10.     CANCELLATION.

         All Securities surrendered for payment, purchase, conversion,
redemption or registration of transfer or exchange for the Securities shall, if
surrendered to any Person other than the Trustee, be delivered to the Trustee
and shall be promptly canceled by it. The Company may at any time deliver to the
Trustee for cancellation any Securities previously authenticated and delivered
hereunder which the Company may have acquired in any manner whatsoever, and all
Securities so delivered shall be promptly canceled by the Trustee. The Company
may not issue new Securities to replace Securities it has paid for or delivered
to the Trustee for cancellation or that any Holder has converted pursuant to
Article 11 hereof. No Securities shall be authenticated in lieu of or in
exchange for any Securities canceled as provided in this Section 2.10, except as
expressly permitted by this Indenture. All canceled Securities held by the
Trustee shall be disposed of by the Trustee in accordance with its customary
procedures.

         SECTION 2.11.     PERSONS DEEMED OWNERS.

         Prior to due presentment of a Security for registration of transfer,
the Company, the Trustee and any agent of the Company or the Trustee may treat
the Person in whose name such Security is registered as the owner of such
Security for the purpose of receiving payment of Principal Amount, Issue Price,
accrued Original Issue Discount, Redemption Price, Purchase Price, Fundamental
Change Purchase Price, Liquidated Damages, if any, and interest, if any, in
respect thereof, for the purpose of conversion and for all other purposes
whatsoever, whether or not such Security be overdue, and none of the Company,
the Trustee or any agent of the Company or the Trustee shall be affected by
notice to the contrary.

         SECTION 2.12.     CUSIP NUMBERS.

         The Company in issuing the Securities may use "CUSIP" numbers (if then
generally in use), and, if so, the Trustee shall use "CUSIP" numbers in notices
of redemption as a convenience to Holders; PROVIDED, that any such notice may
state that no representation is made as to the correctness of such numbers
either as printed on the Securities or as contained in any notice of redemption
and that reliance may be placed only on the other identification numbers printed
on the Securities, and any such redemption shall not be affected by any defect
in or omission of such numbers. The Company will promptly notify the Trustee of
any change in the "CUSIP" numbers.

                                   ARTICLE 3.
                           REDEMPTION AND REPURCHASES

         SECTION 3.01.     RIGHT TO REDEEM; NOTICES TO TRUSTEE.

         The Company, at its option, may redeem the Securities in accordance
with the provisions of paragraphs 5 and 7 of the Securities. If the Company
elects to redeem Securities pursuant to

                                       17
<PAGE>   24

paragraph 5 of the Securities, it shall notify the Trustee in writing of the
Redemption Date, the Principal Amount of Securities to be redeemed and the
Redemption Price. The Company shall give the notice to the Trustee provided for
in this Section 3.01 in the case of any redemption of the Securities, at least
20 days before the Redemption Date unless a shorter notice shall be satisfactory
to the Trustee.

         The Company may, upon at least 30 days' notice given to the Holders, on
one or more occasions, elect to extend the period during which the Company
cannot redeem any of the Securities pursuant to paragraph 5 of the Securities.
Such extension period will be as designated in such notice of extension. Each
such election, once made, shall be irrevocable.

         SECTION 3.02.     SELECTION OF SECURITIES TO BE REDEEMED.

         If less than all the Securities held in definitive form are to be
redeemed pursuant to Section 3.01, the Trustee shall select the definitive
Securities to be redeemed pro rata or by lot or by another method the Trustee
considers fair and appropriate (as long as such method is not prohibited by the
rules of any securities exchange or quotation system on which the Securities are
then listed or quoted). The Trustee shall make the selection at least 18 days,
but not more than 65 days, before the Redemption Date from outstanding
definitive Securities not previously called for redemption. The Trustee may
select for redemption portions of the Principal Amount of Securities that have
denominations larger than $1,000. Securities and portions of them the Trustee
selects shall be in Principal Amounts of $1,000 or an integral multiple of
$1,000. Except as expressly stated otherwise, provisions of this Indenture that
apply to definitive Securities called for redemption also apply to portions of
definitive Securities called for redemption. The Trustee shall notify the
Company promptly of the definitive Securities or portions of definitive
Securities to be redeemed.

         Any interest in a Security held in global form by and registered in the
name of the Depositary or its nominee to be redeemed in whole or in part will be
redeemed in accordance with the procedures of the Depositary.

         If any Security selected for partial redemption is converted in part
before termination of the conversion right with respect to the portion of the
Security so selected, the converted portion of such Security shall be deemed (so
far as may be) to be the portion selected for redemption. Securities which have
been converted during a selection of Securities to be redeemed may be treated by
the Trustee as outstanding for the purpose of such selection.

         SECTION 3.03.     NOTICE OF REDEMPTION.

         At least 15 days but not more than 60 days before a Redemption Date,
the Company shall mail a notice of redemption by first-class mail, postage
prepaid, to each Holder of Securities to be redeemed.

         The notice shall identify the Securities to be redeemed and shall
state:

                  (1)      the Redemption Date;

                                       18
<PAGE>   25

                  (2)      the Redemption Price;

                  (3)      the Conversion Rate;

                  (4)      the name and address of the Paying Agent and
Conversion Agent;

                  (5)      that Securities called for redemption may be
converted at any time before the close of business on the last Trading Day
prior to the Redemption Date;

                  (6)      that Holders who want to convert Securities must
satisfy the requirements set forth in paragraph 9 of the Securities;

                  (7)      that Securities called for redemption must be
surrendered to the Paying Agent to collect the Redemption Price;

                  (8)      if fewer than all the outstanding Securities are to
be redeemed, the certificate numbers and Principal Amounts of the particular
Securities to be redeemed;

                  (9)      that Original Issue Discount, Liquidated Damages, if
any, and interest, if any, on Securities called for redemption will cease to
accrue on and after the Redemption Date; and

                  (10)     the CUSIP number or numbers for the Securities.

The notice, if mailed in the manner herein provided, shall be conclusively
presumed to have been duly given, whether or not the Holder receives such
notice. In any case, failure to give such notice by mail or any defect in the
notice to the Holder of any Security designated for redemption as a whole or in
part shall not affect the validity of the proceedings for the redemption of any
other Security.

         At the Company's request, the Trustee shall give the notice of
redemption in the Company's name and at the Company's expense.

         SECTION 3.04.     EFFECT OF NOTICE OF REDEMPTION.

         Once notice of redemption is given, pursuant to Section 3.03 hereof,
Securities called for redemption become due and payable on the Redemption Date
and at the Redemption Price stated in the notice, together with Liquidated
Damages, if any, except for Securities which are converted in accordance with
the terms of this Indenture.

         Upon the later of the Redemption Date or the date such Securities are
surrendered to the Paying Agent, such Securities shall be paid at the Redemption
Price stated in the notice.

                                       19
<PAGE>   26

         SECTION 3.05.     DEPOSIT OF REDEMPTION PRICE.

         Prior to 10 a.m., New York City time, on the Redemption Date, the
Company shall deposit with the Paying Agent (or if the Company or an Affiliate
of the Company is the Paying Agent, shall segregate and hold in trust) cash
sufficient to pay the Redemption Price of all Securities to be redeemed on that
date other than Securities or portions of Securities called for redemption which
prior thereto have been delivered by the Company to the Trustee for cancellation
or have been converted into Common Stock, together with Liquidated Damages, if
any, and on or after the Redemption Date (unless the Company shall default in
the payment of the Securities at the Redemption Price), Original Issue Discount,
Liquidated Damages, if any, and interest, if any, on the Securities or portion
of Securities called for redemption shall cease to accrue and such Securities
shall cease after the close of business on the Trading Day immediately preceding
the Redemption Date to be convertible into Common Stock and, except as provided
in Section 8.02 hereof, to be entitled to any benefit or security under this
Indenture, and the Holders thereof shall have no right in respect of such
Securities except the right to receive the Redemption Price, Liquidated Damages,
if any, thereof and unpaid interest to (but excluding) the Redemption Date. The
Paying Agent shall as promptly as practicable return to the Company any money,
with interest, if any, thereon, not required for that purpose because of
conversion of Securities. If such money is then held by the Company in trust and
is not required for such purpose, it shall be discharged from such trust.

         SECTION 3.06.     SECURITIES REDEEMED IN PART.

         Upon surrender of a Security that is redeemed in part, the Company
shall execute and the Trustee shall authenticate and deliver to the Holder a new
Security in an authorized denomination equal in Principal Amount to the
unredeemed portion of the Security surrendered.

         SECTION 3.07.     CONVERSION ARRANGEMENT ON CALL FOR REDEMPTION.

         In connection with any redemption of Securities, the Company may
arrange for the purchase and conversion into Common Stock of any Securities
called for redemption by an agreement with one or more investment bankers or
other purchasers to purchase such Securities by paying to the Paying Agent in
trust for the Holders, on or before the close of business on the Redemption
Date, an amount that, together with any amounts deposited with the Paying Agent
by the Company for the redemption of the Securities, is not less than the
Redemption Price to the Redemption Date, of such Securities. Notwithstanding
anything to the contrary contained in this Article 3, the obligation of the
Company to pay the Redemption Price of such Securities shall be deemed to be
satisfied and discharged to the extent such amount is so paid by such
purchasers. If such an agreement is entered into, any Securities not duly
surrendered for conversion by the Holders thereof may, at the option of the
Company, be deemed, to the fullest extent permitted by law, acquired by such
purchasers from such Holders and (notwithstanding anything to the contrary
contained in Article 11) surrendered by such purchasers for conversion, all
immediately prior to the close of business on the Redemption Date, subject to
payment of the above amount as aforesaid. The Paying Agent shall hold and pay to
the Holders whose Securities are selected for redemption any such amount paid to
it in the same manner as it would money deposited with

                                       20
<PAGE>   27

it by the Company for the redemption of Securities. Without the Paying Agent's
prior written consent, no arrangement between the Company and such purchasers
for the purchase and conversion of any Securities shall increase or otherwise
affect any of the powers, duties, responsibilities or obligations of the Paying
Agent as set forth in this Indenture, and the Company agrees to indemnify the
Paying Agent from, and hold it harmless against, any loss, liability or expense
arising out of or in connection with any such arrangement for the purchase and
conversion of any Securities between the Company and such purchasers, including
the costs and expenses incurred by the Paying Agent in the defense of any claim
or liability arising out of or in connection with the exercise or performance of
any of its powers, duties, responsibilities or obligations under this Indenture.

         SECTION 3.08.     REPURCHASE OF SECURITIES AT OPTION OF THE HOLDER.

         (a) GENERAL. Securities shall be repurchased by the Company pursuant to
paragraph 6 of the Securities as of February 5, 2006, February 5, 2011 and
February 5, 2016 (each, a "REPURCHASE DATE"), at the purchase price specified
therein (each, a "PURCHASE PRICE"), together with Liquidated Damages, if any, at
the option of the Holder thereof, upon:

                  (1) delivery to the Paying Agent by the Holder of a written
notice of purchase (a "REPURCHASE NOTICE") at any time from the opening of
business on the date that is 20 Business Days prior to a Repurchase Date until
the close of business on such Repurchase Date, stating:

                           (A) the certificate number of any Security in
certificated form which the Holder will deliver to be repurchased;

                           (B) the portion of the Principal Amount of the
Security which the Holder will deliver to be repurchased, which portion must be
$1,000 in Principal Amount or a multiple thereof;

                           (C) that such Security shall be repurchased as of the
Repurchase Date pursuant to the terms and conditions specified in paragraph 6 of
the Securities and in this Indenture; and

                           (D) if the Company elects, pursuant to a Company

Notice, to pay the Purchase Price to be paid as of such Repurchase Date, in
whole or in part, in Common Stock but such portion of the Purchase Price shall
ultimately be payable to such Holder in cash because any of the conditions to
the payment of the Purchase Price in Common Stock are not satisfied prior to or
on the Repurchase Date, as set forth in Section 3.08(d) hereof, whether such
Holder elects (x) to withdraw such Repurchase Notice as to some or all of the
Securities to which such Repurchase Notice relates (stating the Principal Amount
and certificate numbers of any certificated Securities as to which such
withdrawal shall relate), or (y) to receive cash in respect of the entire
Purchase Price for all Securities (or portions thereof) to which such Repurchase
Notice relates; and

                                       21
<PAGE>   28

                  (2) delivery of such Security to the Paying Agent prior to, on
or after the Repurchase Date (together with all necessary endorsements) at the
offices of the Paying Agent, such delivery being a condition to receipt by the
Holder of the Purchase Price therefor; PROVIDED, HOWEVER, that such Purchase
Price shall be so paid pursuant to this Section 3.08 only if the Security so
delivered to the Paying Agent shall conform in all respects to the description
thereof in the related Repurchase Notice.

         If a Holder, in such Holder's Repurchase Notice (and, in any written
notice of withdrawal of a portion of such Holder's Securities previously
submitted for repurchase pursuant to a Repurchase Notice, the portion that
remains subject to the Repurchase Notice), fails to indicate such Holder's
choice with respect to the election set forth in clause (D) of Section
3.08(a)(1), such Holder shall be deemed to have elected to receive cash in
respect of the entire Purchase Price for all Securities subject to such
Repurchase Notice in the circumstances set forth in such clause (D).

         The Company shall purchase from the Holder thereof, pursuant to this
Section 3.08, a portion of a Security if the Principal Amount of such portion is
$1,000 or an integral multiple of $1,000. Provisions of this Indenture that
apply to the purchase of all of a Security also apply to the repurchase of such
portion of such Security.

         Any purchase by the Company contemplated pursuant to the provisions of
this Section 3.08 shall be consummated by the delivery of the consideration to
be received by the Holder promptly following the later of the Repurchase Date
and the time of delivery of the Security.

         Notwithstanding anything herein to the contrary, any Holder delivering
to the Paying Agent the Repurchase Notice contemplated by this Section 3.08(a)
shall have the right at any time prior to the close of business on the
Repurchase Date to withdraw such Repurchase Notice by delivery of a written
notice of withdrawal to the Paying Agent in accordance with Section 3.10 hereof.

         The Paying Agent shall promptly notify the Company of the receipt by it
of any Repurchase Notice or written notice of withdrawal thereof.

         (b) COMPANY'S RIGHT TO ELECT MANNER OF PAYMENT OF PURCHASE PRICE. The
Company may elect with respect to any Repurchase Date to pay the Purchase Price
in respect of the Securities to be purchased pursuant to Section 3.08(a) as of
such Repurchase Date, in U.S. legal tender ("cash") or Common Stock, or in any
combination of cash and Common Stock, subject to the conditions set forth in
Sections 3.08(c) and (d). The Company shall designate, in the Company Notice
delivered pursuant to Section 3.08(e), whether the Company will repurchase the
Securities for cash or Common Stock, or, if a combination thereof, the
percentages of the Purchase Price of Securities in respect of which it will pay
in cash and/or Common Stock; PROVIDED that the Company will pay cash for
fractional interests in shares of Common Stock. For purposes of determining the
existence of potential fractional interests, all Securities subject to
repurchase by the Company held by a Holder shall be

                                       22
<PAGE>   29

considered together (no matter how many separate certificates are to be
presented). Each Holder whose Securities are repurchased pursuant to this
Section 3.08 shall receive the same percentage of cash and/or Common Stock in
payment of the Purchase Price for such Securities, except (i) as provided in
Section 3.08(d) with regard to the payment of cash in lieu of fractional
interests in shares of Common Stock and (ii) in the event that the Company is
unable to repurchase the Securities of a Holder or Holders for Common Stock
because any necessary qualifications or registrations of the Common Stock under
applicable federal, state or foreign securities laws cannot be obtained, the
Company may repurchase the Securities of such Holder or Holders for cash. The
Company may not change its election with respect to the consideration (or
components or percentages of components thereof) to be paid once the Company has
given its Company Notice to Holders except pursuant to this Section 3.08(b) or
Section 3.08(d).

         At least one Business Day before the Company Notice Date (as defined in
Section 3.08(c)), the Company shall deliver an Officers' Certificate to the
Trustee specifying:

         (i) the manner of payment selected by the Company,

         (ii) the information required by Section 3.08(e),

         (iii) if the Company elects to pay the Purchase Price, or a specified
percentage thereof, in Common Stock, that the conditions to such manner of
payment set forth in Section 3.08(d) have been or will be complied with, and

         (iv) whether the Company desires the Trustee to give the Company Notice
required by Section 3.08(e).

         (c) REPURCHASE WITH CASH. At the option of the Company, the Purchase
Price of Securities in respect of which a Repurchase Notice pursuant to Section
3.08(a) has been given, or a specified percentage thereof, may be paid by the
Company with cash equal to the aggregate Purchase Price, or such specified
percentage thereof, as the case may be, of such Securities. If the Company
elects to repurchase all or a portion of Securities with cash, a Company Notice
as provided in Section 3.08(e) shall be sent to Holders (and to beneficial
owners as required by applicable law) not less than 20 Business Days (the
"COMPANY NOTICE DATE") prior to the Repurchase Date.

         (d) PAYMENT BY ISSUANCE OF COMMON STOCK. At the option of the Company,
the Purchase Price of Securities in respect of which a Repurchase Notice
pursuant to Section 3.08(a) has been given, or a specified percentage thereof,
may be paid by the Company by the issuance of a number of shares of Common Stock
equal to the quotient obtained by dividing (i) the amount of cash to which the
Holders would have been entitled had the Company elected to pay all or such
specified percentage, as the case may be, of the Purchase Price of such
Securities in cash by (ii) the Market Price of a share of Common Stock as of the
applicable Repurchase Date, subject to the next succeeding paragraph.

         The Company will not issue a fractional share of Common Stock in
payment of the Purchase Price. Instead the Company will pay cash for the current
market value of the fractional

                                       23
<PAGE>   30

share. The current market value of a fraction of a share shall be determined by
multiplying the Market Price by such fraction and rounding the product to the
nearest whole cent. It is understood that if a Holder elects to have more than
one Security repurchased, the number of shares of Common Stock shall be based on
the aggregate amount of Securities to be repurchased.

         If the Company elects to repurchase all or a portion of the Securities
by the issuance of shares of Common Stock, a Company Notice as provided in
Section 3.08(e) shall be sent to the Holders (and to beneficial owners as
required by applicable law) not later than the Company Notice Date.

         The Company's right to exercise its election to repurchase the
Securities pursuant to Section 3.08 through the issuance of shares of Common
Stock shall be conditioned upon:

               (i) the Company having given timely Company Notice of election to
purchase all or a specified percentage of the Securities with Common Stock as
provided herein;

               (ii) the registration of the shares of Common Stock to be issued
in respect of the payment of the specified percentage of the Purchase Price
under the Securities Act, unless the shares of Common Stock so issued can be
freely resold by the Holder (unless such Holder is the Company or an Affiliate
of the Company) receiving such shares without registration under the Securities
Act;

               (iii) any necessary qualification or registration under
applicable state securities laws or the availability of an exemption from such
qualification and registration; and

               (iv) the receipt by the Trustee of an Officers' Certificate and
an Opinion of Counsel each stating that (A) the terms of the issuance of the
Common Stock are in conformity with this Indenture and (B) the shares of Common
Stock to be issued by the Company in payment of the specified percentage of the
Purchase Price in respect of Securities have been duly authorized and, when
issued and delivered pursuant to the terms of this Indenture in payment of the
specified percentage of the Purchase Price in respect of Securities, will be
validly issued, fully paid and nonassessable, and, in the case of such Officers'
Certificate, stating that conditions (i), (ii) and (iii) above have been
satisfied and, in the case of such Opinion of Counsel, stating that conditions
(ii) and (iii) above have been satisfied.

         Such Officers' Certificate shall also set forth the number of shares of
Common Stock to be issued for each $1,000 Principal Amount of Securities and the
Sale Price of the Common Stock on each Trading Day during the period during
which the Market Price is calculated and ending on the Repurchase Date, and the
Company shall publish such information as soon as practicable in a daily
newspaper of national circulation. The Company may elect to pay the Purchase
Price (or any portion thereof) in Common Stock only if the information necessary
to calculate the Market Price is reported in a daily newspaper of national
circulation. If such conditions are not satisfied with respect to a Holder or
Holders prior to or on the Repurchase Date and the Company elected to repurchase
the Securities to be repurchased as of such Repurchase Date pursuant to this
Section 3.08 through the issuance of shares of Common Stock,

                                       24
<PAGE>   31

the Company shall pay the entire Purchase Price in respect of such Securities of
such Holder or Holders in cash.

         (e) NOTICE OF ELECTION. The Company's notices of election to repurchase
with cash or Common Stock, or any combination thereof, shall be sent to the
Holders (and to beneficial owners as required by applicable law) in the manner
provided in Section 13.02 hereof at the time specified in Section 3.08(c) or (d)
hereof, as applicable (each, a "COMPANY NOTICE"). Such Company Notices shall
state the manner of payment elected and shall contain the following information:

         In the event the Company has elected to pay a Purchase Price (or a
specified percentage thereof) with Common Stock, the Company Notice shall:

                  (1) state that each Holder will receive Common Stock with a
Market Price determined as of a specified date prior to the Repurchase Date
equal to such specified percentage of the Purchase Price of the Securities held
by such Holder (except any cash amount to be paid in lieu of a fractional
share); and

                  (2) set forth the method of calculating the Market Price and
state that because the Market Price of Common Stock will be determined prior to
the Repurchase Date, the Holders will bear the market risk with respect to the
value of the Common Stock to be received from the date such Market Price is
determined to the Repurchase Date.

         In any case, each Company Notice shall include a form of Repurchase
Notice to be completed by a Holder and shall state:

         (i) the Purchase Price and Conversion Rate;

         (ii) the name and address of the Paying Agent and the Conversion Agent;

         (iii) that Securities as to which a Repurchase Notice has been given
may be converted only if the applicable Repurchase Notice has been withdrawn in
accordance with the terms of this Indenture;

         (iv) that Securities must be surrendered to the Paying Agent to collect
payment;

         (v) that the Purchase Price for any Security as to which a Repurchase
Notice has been given and not withdrawn will be paid promptly following the
later of the Repurchase Date and the time of surrender of such Security as
described in clause (iv) above;

         (vi) the procedures the Holder must follow under this Section 3.08;

         (vii) briefly, the conversion rights of the Securities; and

                                       25
<PAGE>   32
                  (viii) the procedures for withdrawing a Repurchase Notice
(including, without limitation, for a conditional withdrawal pursuant to the
terms of Section 3.08(a)(1)(D) or Section 3.10 hereof).

         At the Company's request, the Trustee shall give the Company Notice in
the Company's name and at the Company's expense; PROVIDED, HOWEVER, that, in all
cases, the text of the Company Notice shall be prepared by the Company.

         (f) COVENANTS OF THE COMPANY. All shares of Common Stock delivered upon
conversion or repurchase of the Securities shall be newly issued shares or
treasury shares, shall be fully paid and nonassessable and shall be free from
preemptive rights and free of any lien or adverse claim. Such shares shall bear
any legend required by Section 2.06(d) hereof.

         The Company shall use its reasonable best efforts to list or cause to
have quoted all such shares of Common Stock on each United States national
securities exchange or over-the-counter or other domestic market on which the
Common Stock is then listed or quoted.

         (g) PROCEDURE UPON PURCHASE. On the Business Day following the
Repurchase Date, the Company shall deposit with the Paying Agent cash (in
respect of a cash purchase under Section 3.08(c) hereof or for fractional
interests, as applicable), or shares of Common Stock, or a combination thereof,
as applicable, sufficient to pay the aggregate Purchase Price in respect of the
Securities to be repurchased pursuant to this Section 3.08, plus Liquidated
Damages, if any. As soon as practicable after the Repurchase Date, the Company
shall deliver to each Holder entitled to receive Common Stock, through the
Paying Agent, a certificate for the number of full shares of Common Stock, as
applicable, issuable in payment of such Purchase Price and cash in lieu of any
fractional interests. The Person in whose name the certificate for Common Stock
is registered shall be treated as a holder of record following the Repurchase
Date. No payment or adjustment will be made for dividends on the Common Stock
the record date for which occurred on or prior to the Repurchase Date.

         (h) TAXES. If a Holder of a Security is paid in Common Stock, the
Company shall pay any documentary, stamp or similar issue or transfer tax due on
such issue of shares of Common Stock. However, the Holder shall pay any such tax
which is due because the Holder requests the shares of Common Stock to be issued
in a name other than the Holder's name. The Paying Agent may refuse to deliver
the certificates representing the Common Stock being issued in a name other than
the Holder's name until the Paying Agent receives a sum sufficient to pay any
tax which will be due because the shares of Common Stock are to be issued in a
name other than the Holder's name. Nothing herein shall preclude any income tax
withholding required by law or regulations.

         SECTION 3.09. REPURCHASE AT OPTION OF THE HOLDER UPON A FUNDAMENTAL
CHANGE.

         (a) If a Fundamental Change shall occur at any time prior to February
5, 2021, each Holder of Securities shall have the right, at such Holder's
option, to require the

                                       26
<PAGE>   33

Company to repurchase any or all of Holder's Securities on the date that is 30
days after the date of the Company's notice of such Fundamental Change (the
"FUNDAMENTAL CHANGE REPURCHASE DATE") (or if such date is not a Business Day,
the next succeeding Business Day). The Securities may be repurchased in integral
multiples of $1,000 of Principal Amount. The Company shall repurchase such
Securities at a price (the "FUNDAMENTAL CHANGE PURCHASE PRICE") equal to the
Issue Price plus accrued Original Issue Discount, Liquidated Damages, if any,
and interest, if any, to the Fundamental Change Repurchase Date.

                  (b) The Company, or at its request (which must be received by
the Trustee at least three Business Days prior to the date the Trustee is
requested to give such notice as described below) the Trustee in the name of and
at the expense of the Company, shall mail to all Holders of record of the
Securities a notice (a "FUNDAMENTAL CHANGE REPURCHASE NOTICE") of the occurrence
of a Fundamental Change and of the repurchase right arising as a result thereof
on or before the thirtieth day after the occurrence of such Fundamental Change.
The Company shall promptly furnish the Trustee a copy of such notice.

                  (c) For a Security to be so repurchased at the option of the
Holder, the Paying Agent must receive such Security with the form entitled
"Option to Elect Repurchase Upon a Fundamental Change" on the reverse thereof
duly completed, together with such Security duly endorsed for transfer, on or
before the 30th day after the date of the Fundamental Change Repurchase Notice
(or if such 30th day is not a Business Day, the immediately preceding Business
Day). All questions as to the validity, eligibility (including time of receipt)
and acceptance of any Security for repurchase shall be determined by the
Company, whose determination shall be final and binding.

         SECTION 3.10. EFFECT OF REPURCHASE NOTICE OR FUNDAMENTAL CHANGE
REPURCHASE NOTICE.

         Upon receipt by the Company of the Repurchase Notice or Option to Elect
Repurchase Upon a Fundamental Change specified in Section 3.08(a) hereof or
Section 3.09(c) hereof, as applicable, the Holder of the Security in respect of
which such Repurchase Notice or Option to Elect Repurchase Upon a Fundamental
Change, as the case may be, was given shall (unless such Repurchase Notice or
Option to Elect Repurchase Upon a Fundamental Change is withdrawn as specified
in the following two paragraphs) thereafter be entitled to receive solely the
Purchase Price or Fundamental Change Purchase Price, as the case may be, with
respect to such Security, together with Liquidated Damages, if any. Such
Purchase Price or Fundamental Change Purchase Price, together with Liquidated
Damages, if any, shall be paid to such Holder promptly following the later of
(x) the Repurchase Date or the Fundamental Change Repurchase Date, as the case
may be, with respect to such Security (provided the conditions in Section
3.08(a) hereof or Section 3.09(c) hereof, as applicable, have been satisfied)
and (y) the time of delivery of such Security to the Paying Agent by the Holder
thereof in the manner required by Section 3.08(a) hereof or Section 3.09(c)
hereof, as applicable. Securities in respect of which a Repurchase Notice or
Option to Elect Repurchase Upon a Fundamental Change, as the case may be, has
been given by the Holder thereof may not be converted for shares of Common Stock
on or after the date of the delivery of such Repurchase Notice (or Option to
Elect Repurchase Upon a Fundamental Change, as the case may be), unless such
Repurchase Notice (or Option to Elect

                                       27
<PAGE>   34

Repurchase Upon a Fundamental Change, as the case may be) has first been validly
withdrawn as specified in the following two paragraphs.

         A Repurchase Notice or Option to Elect Repurchase Upon a Fundamental
Change, as the case may be, may be withdrawn by means of a written notice of
withdrawal delivered to the office of the Paying Agent at any time prior to the
close of business on the Repurchase Date or the Fundamental Change Repurchase
Date, as the case may be, to which it relates specifying:

                  (1) the certificate number of any certificated Security in
respect of which such notice of withdrawal is being submitted,

                  (2) the Principal Amount of the Security with respect to which
such notice of withdrawal is being submitted, and

                  (3) the Principal Amount, if any, of such Security which
remains subject to the original Repurchase Notice or Option to Elect Repurchase
Upon a Fundamental Change, as the case may be, and which has been or will be
delivered for purchase or redemption by the Company.

         A written notice of withdrawal of a Repurchase Notice may be in the
form of (i) a conditional withdrawal contained in a Repurchase Notice pursuant
to the terms of Section 3.08(a)(1)(D) hereof or (ii) a conditional withdrawal
containing the information set forth in Section 3.08(a)(1)(D) hereof and the
preceding paragraph and contained in a written notice of withdrawal delivered to
the Paying Agent as set forth in the preceding paragraph.

         There shall be no repurchase of any Securities pursuant to Section 3.08
hereof (other than through the issuance of Common Stock in payment of the
Purchase Price, including cash in lieu of any fractional shares) or repurchase
pursuant to Section 3.09 hereof if there has occurred (prior to, on or after, as
the case may be, the giving, by the Holders of such Securities, of the required
Repurchase Notice or Option to Elect Repurchase Upon a Fundamental Change, as
the case may be) and is continuing an Event of Default (other than a default in
the payment of the Purchase Price or Fundamental Change Purchase Price, as the
case may be, with respect to such Securities).

         SECTION 3.11. DEPOSIT OF PURCHASE PRICE OR FUNDAMENTAL CHANGE PURCHASE
PRICE.

         At or before 10 a.m., New York City time, on the Business Day following
a Repurchase Date or a Fundamental Change Repurchase Date, as the case may be,
the Company shall deposit with the Trustee or with the Paying Agent (or, if the
Company or an Affiliate of the Company is acting as the Paying Agent, shall
segregate and hold in trust as provided in Section 2.04 hereof) an amount of
cash and/or securities, if permitted hereunder, sufficient to pay the aggregate
Purchase Price or Fundamental Change Purchase Price, as the case may be, of all
the Securities or portions thereof which are to be purchased as of such
Repurchase Date or Fundamental Change Repurchase Date, as the case may be, plus
Liquidated Damages, if any.

                                       28
<PAGE>   35

         SECTION 3.12.     SECURITIES REPURCHASED IN PART.

         Any Security that is to be repurchased only in part shall be
surrendered at the office of the Paying Agent (with, if the Company or the
Trustee so requires, due endorsement by, or a written instrument of transfer in
form satisfactory to the Company and the Trustee duly executed by, the Holder
thereof or such Holder's attorney duly authorized in writing) and the Company
shall execute and the Trustee shall authenticate and deliver to the Holder of
such Security, without service charge, a new Security or Securities, of any
authorized denomination as requested by such Holder in aggregate Principal
Amount equal to, and in exchange for, the portion of the Principal Amount of the
Security so surrendered which is not repurchased.

         SECTION 3.13. COVENANT TO COMPLY WITH SECURITIES LAWS UPON REPURCHASE
OF SECURITIES.

         In connection with any repurchase of Securities under Section 3.08 or
3.09 hereof, the Company shall (i) comply with Rule 13e-4 (which term, as used
herein, includes any successor provision thereto) under the Exchange Act, if
applicable, (ii) file the related Schedule 13E-4 (or any successor schedule,
form or report) under the Exchange Act, if applicable, and (iii) otherwise
comply with all Federal and state securities laws so as to permit the rights and
obligations under Sections 3.08 and 3.09 to be exercised in the time and in the
manner specified in Sections 3.08 and 3.09.

         SECTION 3.14.     REPAYMENT TO THE COMPANY.

         The Trustee and the Paying Agent shall return to the Company any cash
or shares of Common Stock that remain unclaimed as provided in paragraph 14 of
the Securities, together with interest or dividends, if any, thereon, held by
them for the payment of a Purchase Price or Fundamental Change Purchase Price,
as the case may be, together with Liquidated Damages, if any; PROVIDED, HOWEVER,
that to the extent that the aggregate amount of cash or shares of Common Stock
deposited by the Company pursuant to Section 3.11 hereof exceeds the aggregate
Purchase Price or Fundamental Change Purchase Price, as the case may be, of the
Securities or portions thereof which the Company is obligated to repurchase as
of the Repurchase Date or Fundamental Change Repurchase Date, as the case may
be, together with Liquidated Damages, if any, then promptly after the Business
Day following the Repurchase Date or Fundamental Change Repurchase Date, as the
case may be, the Trustee and the Paying Agent shall return any such excess to
the Company together with interest or dividends, if any, thereon.

                                   ARTICLE 4.
                                   COVENANTS

         SECTION 4.01.     PAYMENT OF SECURITIES.

         The Company shall promptly pay or cause to be paid all payments in
respect of the Securities on the dates and in the manner provided in the
Securities or pursuant to this Indenture. Principal Amount, Issue Price, accrued
Original Issue Discount, Redemption Price, Purchase Price, Fundamental Change
Purchase Price, Liquidated Damages, if any, and interest, if any,

                                       29
<PAGE>   36

shall be considered paid on the applicable date due or, in the case of a
Purchase Price or Fundamental Change Purchase Price, on the Business Day
following the applicable Repurchase Date or Fundamental Change Repurchase Date,
as the case may be, if on such date the Trustee or the Paying Agent holds, in
accordance with this Indenture, cash or securities, if permitted hereunder,
sufficient to pay all such amount then due.

         The Company shall pay interest on overdue amounts at the rate set forth
in paragraph 1 of the Securities and it shall pay interest on overdue interest
at the same rate compounded semiannually (to the extent that the payment of such
interest shall be legally enforceable), which interest on overdue interest shall
accrue from the date such amounts became overdue and shall be in lieu of, and
not in addition to, the continued accrual of Original Issue Discount.

         SECTION 4.02.     FINANCIAL INFORMATION; SEC REPORTS.

         The Company will deliver to the Trustee (a) as soon as available and in
any event within 120 days after the end of each fiscal year of the Company (i) a
consolidated balance sheet of the Company and its subsidiaries as of the end of
such fiscal year and the related consolidated statements of operations,
stockholders' equity and cash flows for such fiscal year, all reported on by an
independent public accountant of nationally recognized standing and (ii) a
report containing a management's discussion and analysis of the financial
condition and results of operations and a description of the business and
properties of the Company and (b) as soon as available and in any event within
60 days after the end of each of the first three quarters of each fiscal year of
the Company (i) an unaudited consolidated financial report for such quarter and
(ii) a report containing a management's discussion and analysis of the financial
condition and results of operations of the Company; PROVIDED that the foregoing
shall not be required for any fiscal year or quarter, as the case may be, with
respect to which the Company files or expects to file with the Trustee an annual
report or quarterly report, as the case may be, pursuant to the third paragraph
of this Section 4.02.

         At any time the Company is not subject to either Section 13 or 15(d) of
the Exchange Act, the Company shall at the request of any Holder (or holders of
Common Stock issued upon conversion of the Securities) provide to such Holder
(or holders of such Common Stock) and any prospective purchaser designated by
such Holders (or holders of such Common Stock), as the case may be, such
information, if any, required by Rule 144A(d)(4) under the Securities Act.

         The Company shall file with the Trustee, within 15 days after it files
such annual and quarterly reports, information, documents and other reports with
the SEC, copies of its annual report and of the information, documents and other
reports (or copies of such portions of any of the foregoing as the SEC may by
rules and regulations prescribe) which the Company is required to file with the
SEC pursuant to Section 13 or 15(d) of the Exchange Act.

         Delivery of such reports, information and documents to the Trustee is
for informational purposes only and the Trustee's receipt of such shall not
constitute constructive notice of any information contained therein or
determinable from the information contained therein, including the Company's
compliance with any of its covenants hereunder (as to which the Trustee is
entitled to rely exclusively on Officers' Certificates).

                                       30
<PAGE>   37

         SECTION 4.03.     COMPLIANCE CERTIFICATE.

         The Company shall deliver to the Trustee, within 120 days after the end
of each fiscal year of the Company, an Officers' Certificate in which one of the
two Officers signing such certificate is either the principal executive officer,
principal financial officer or principal accounting officer of the Company,
stating whether or not to the knowledge of the signers thereof the Company is in
default in the performance and observance of any of the terms, provisions and
conditions of this Indenture (without regard to any period of grace or
requirement of notice provided hereunder) and, if the Company shall be in
default, specifying all such defaults and the nature and status thereof of which
the signers may have knowledge.

         The Company will deliver to the Trustee, as soon as possible and in any
event within five days, upon becoming aware of any default or any Event of
Default, an Officers' Certificate specifying with particularity such Default or
Event of Default and further stating what action the Company has taken, is
taking or proposes to take with respect thereto.

         Any notice required to be given under this Section 4.03 shall be
delivered to the Trustee at its Corporate Trust Office.

         SECTION 4.04.     FURTHER INSTRUMENTS AND ACTS.

         Upon request of the Trustee, the Company will execute and deliver such
further instruments and do such further acts as may be reasonably necessary or
proper to carry out more effectively the purposes of this Indenture.

         SECTION 4.05.     MAINTENANCE OF OFFICE OR AGENCY.

         The Company will appoint in the Borough of Manhattan, The City of New
York, an office or agency where Securities may be presented or surrendered for
payment, where Securities may be surrendered for registration of transfer,
exchange, purchase, redemption or conversion and where notices and demands to or
upon the Company in respect of the Securities and this Indenture may be served.
The office or agency of the Trustee in the Borough of Manhattan, The City of New
York, which on the date hereof is located at 14 Wall Street, 8th Floor, Window
2, New York, New York, and shall be the office or agency for all of the
aforesaid purposes unless the Company shall appoint some other office or agency
for such purposes and shall give prompt written notice to the Trustee of the
location, and any change in the location, of such other office or agency. If at
any time the Company shall fail to maintain any such required office or agency
or shall fail to furnish the Trustee with the address thereof, such
presentations, surrenders, notices and demands may be made or served at the
Corporate Trust Office.

         The Company may also from time to time designate one or more other
offices or agencies where the Securities may be presented or surrendered for any
or all such purposes and may from time to time rescind such designations;
PROVIDED, HOWEVER, that no such designation or rescission shall in any manner
relieve the Company of its obligation to maintain an office or agency in the
Borough of Manhattan, The City of New York, for such purposes.

                                       31
<PAGE>   38

         SECTION 4.06.     EXISTENCE.

         Subject to Article 5 hereof, the Company will do or cause to be done
all things necessary to preserve and keep in full force and effect its corporate
existence under the laws of its jurisdiction of incorporation and rights
(charter and statutory); PROVIDED, HOWEVER, that the Company shall not be
required to preserve any such right if the Company shall determine that the
maintenance thereof is no longer desirable in the conduct of the business of the
Company and that the loss thereof is not disadvantageous in any material respect
to the Holders.

         SECTION 4.07.     CALCULATION OF ORIGINAL ISSUE DISCOUNT.

         The Company shall file with the Trustee promptly at the end of each
calendar year (i) a written notice specifying the amount of Original Issue
Discount (including daily rates and accrual periods) accrued on the outstanding
Securities as of the end of such year and (ii) such other specific information
relating to such Original Issue Discount as may then be relevant under the
Internal Revenue Code of 1986, as amended from time to time.

         SECTION 4.08.     REGISTRATION RIGHTS.

         (a) The Company agrees that the Holders (and any Person that has a
beneficial interest in a Security) from time to time of Registrable Securities
(as such term is defined in the Registration Rights Agreement) are entitled to
the benefits of the Registration Rights Agreement. Pursuant to the Registration
Rights Agreement, the Company has agreed for the benefit of the Holders from
time to time of Registrable Securities, at the Company's expense, to use all
reasonable best efforts (i) to file within 90 days after the first date of
original issuance of the Securities, a shelf registration statement (the "SHELF
REGISTRATION STATEMENT") with the Commission with respect to resales of the
Restricted Securities, (ii) to cause such Shelf Registration Statement to be
declared effective by the Commission not later than 180 days after the first
date of original issuance of the Securities, and (iii) to maintain such Shelf
Registration Statement continuously effective under the Securities Act subject
to and in accordance with the terms of the Registration Rights Agreement.
Liquidated damages ("LIQUIDATED DAMAGES") with respect to the Securities shall
be assessed if a Registration Default (as defined in the Registration Rights
Agreement) occurs.

         (b) The Company shall pay Liquidated Damages due pursuant to clause (a)
of this Section 4.08 to the Holders in cash in the amounts and on the dates
specified in the Registration Rights Agreement and in this Indenture.

         Whenever in this Indenture there is mentioned, in any context, any
payment in respect of any Security, such mention shall be deemed to include
mention of the payment of Liquidated Damages provided for in this Section to the
extent that, in such context, Liquidated Damages are, were or would be payable
in respect thereof pursuant to the provisions of this Section 4.08, and express
mention of the payment of Liquidated Damages (if applicable) in any provisions
hereof shall not be construed as excluding Liquidated Damages in those
provisions hereof where such express mention is not made.

                                       32
<PAGE>   39

         If Liquidated Damages become payable to the Holders pursuant to the
Registration Rights Agreement, at least five Business Days prior to the date on
which such Liquidated Damages are payable, the Company shall deliver to the
Trustee a certificate to that effect stating (i) the amount of such Liquidated
Damages that is payable and (ii) the date on which such amount is payable.
Unless and until a Trust Officer receives at the Corporate Trust Office such a
certificate, the Trustee may assume without inquiry that no such amount is
payable.

                                   ARTICLE 5.
                              SUCCESSOR CORPORATION

         SECTION 5.01.     WHEN THE COMPANY MAY MERGE OR TRANSFER ASSETS.

         The Company shall not consolidate with or merge with or into any other
Person (other than in a merger or consolidation in which the Company is the
surviving Person) or convey, transfer or lease its properties and assets
substantially as an entirety to any Person, unless:

                  (i) the Person (if other than the Company) formed by such
consolidation or into which the Company is merged or the Person which acquires
by conveyance, transfer or lease the properties and assets of the Company
substantially as an entirety shall be a corporation, limited liability company,
partnership or trust organized and validly existing under the laws of the United
States or any State thereof or the District of Columbia, and shall expressly
assume by an indenture supplemental hereto, executed and delivered to the
Trustee in form reasonably satisfactory to the Trustee, the due and punctual
payment of the Principal Amount, Issue Price, accrued Original Issue Discount,
Redemption Price, Purchase Price, Fundamental Change Purchase Price, Liquidated
Damages, if any, or interest, if any, on the Securities, according to their
tenor, and the due and punctual performance of all of the covenants and
obligations of the Company under the Securities and this Indenture, and shall
have provided for conversion rights in accordance with this Indenture;

                  (ii) immediately after giving effect to such transaction, no
Default or Event of Default shall have occurred and be continuing; and

                  (iii) the Company shall have delivered to the Trustee an
Officers' Certificate and an Opinion of Counsel, each stating that such
consolidation, merger, conveyance, transfer or lease and, if a supplemental
indenture is required in connection with such transaction, such supplemental
indenture, comply with this Article 5 and that all conditions precedent herein
provided for relating to such transaction have been satisfied.

         The successor Person formed by such consolidation or into which the
Company is merged or the successor Person to which such conveyance, transfer or
lease is made shall succeed to, and be substituted for, and may exercise every
right and power of, the Company under this Indenture with the same effect as if
such successor had been named as the Company herein; and thereafter, except in
the case of a lease, the Company shall be discharged from all obligations and
covenants under this Indenture and the Securities.

                                       33
<PAGE>   40

                                   ARTICLE 6.
                              DEFAULTS AND REMEDIES

         SECTION 6.01.     EVENTS OF DEFAULT.

         An "EVENT OF DEFAULT" occurs if:

                  (1) the Company defaults in the payment of the Principal
Amount, Issue Price, Redemption Price, Purchase Price or a Fundamental Change
Purchase Price on any Security when the same becomes due and payable at its
Stated Maturity, upon redemption, upon declaration, when due for repurchase by
the Company or otherwise, and such default continues for a period of ten days;

                  (2) the Company defaults in the payment of accrued Original
Issue Discount or Liquidated Damages and such default continues for 30 days, or,
after exercise of the option provided for in Section 12.01 hereof following a
Tax Event, the Company defaults in the payment of interest upon any Security
when such interest becomes due and payable, and such default continues for a
period of 30 days;

                  (3) failure of the Company to perform or comply with the
provisions of Section 11.02 hereof, and such failure continues for a period of
20 days;

                  (4) the Company fails to comply with any of its agreements or
covenants in the Securities or this Indenture (other than those referred to in
clauses (1) through (3) above) and such failure continues for 90 days after
receipt by the Company of a Notice of Default;

                  (5) a decree or order by a court having jurisdiction in the
premises shall have been entered adjudging the Company a bankrupt or insolvent,
or approving as properly filed a petition seeking reorganization of the Company
under any Bankruptcy Law, and such decree or order shall have continued
undischarged and unstayed for a period of 90 consecutive days; or a decree or
order of a court having jurisdiction in the premises of the appointment of a
receiver or liquidator or trustee or assignee in bankruptcy or insolvency of the
Company or of its property, or for the winding-up or liquidation of its affairs,
shall have been entered, and such decree or order shall have remained in force
undischarged and unstayed of a period of 90 consecutive days; or

                  (6) the Company shall institute proceedings to be adjudicated
a voluntary bankrupt, or shall consent to the filing of a bankruptcy proceeding
against it, or shall file a petition or answer or consent seeking reorganization
under any Bankruptcy Law, or shall consent to the filing of any such petition,
or shall consent to the appointment of a receiver or liquidator or trustee or
assignee in bankruptcy or insolvency of it or of its property or shall make an
assignment for the benefit of creditors, or shall admit in writing its inability
to pay its debts generally as they become due.

                                       34
<PAGE>   41

         A Default under clause (4) above is not an Event of Default until the
Trustee notifies the Company, or the Holders of at least 25% in aggregate
Principal Amount of the Securities at the time outstanding notify the Company
and the Trustee, of the Default and the Company does not cure such Default (and
such Default is not waived) within the time specified in clause (4) above after
actual receipt of such notice (a "NOTICE OF DEFAULT"). Any such notice must
specify the Default, demand that it be remedied and state that such notice is a
Notice of Default.

         SECTION 6.02.     ACCELERATION.

         If an Event of Default (other than an Event of Default specified in
Section 6.01(5) or (6) hereof) occurs and is continuing, the Trustee by notice
to the Company, or the Holders of at least 25% in aggregate Principal Amount of
the Securities at the time outstanding by notice to the Company and the Trustee,
may declare the Issue Price and accrued Original Issue Discount and Liquidated
Damages, if any (or, if the Securities have been converted to Semiannual Coupon
Debentures, the Restated Principal Amount, plus accrued and unpaid interest) to
the date of declaration on all the Securities to be immediately due and payable.
Upon such a declaration, such Issue Price and accrued Original Issue Discount
and Liquidated Damages, if any (or, if the Securities have been converted to
Semiannual Coupon Debentures, the Restated Principal Amount, plus accrued and
unpaid interest) shall become and be due and payable immediately. If an Event of
Default specified in Section 6.01(5) or (6) hereof occurs and is continuing, the
Issue Price and accrued Original Issue Discount and Liquidated Damages, if any
(or, if the Securities have been converted to Semiannual Coupon Debentures, the
Restated Principal Amount, plus accrued and unpaid interest) on all the
Securities shall become and be immediately due and payable without any
declaration or other act on the part of the Trustee or any Holders. The Holders
of a majority in aggregate Principal Amount of the Securities at the time
outstanding, by notice to the Company and the Trustee (and without notice to any
other Holder), may rescind an acceleration and its consequences if the
rescission would not conflict with any judgment or decree and if all existing
Events of Default have been cured or waived except nonpayment of the Issue Price
and accrued Original Issue Discount (or, if the Securities have been converted
to Semiannual Coupon Debentures, the Restated Principal Amount, plus accrued and
unpaid interest) that have become due solely as a result of acceleration and if
all amounts due to the Trustee under Section 7.07 hereof have been paid. No such
rescission shall affect any subsequent or other Default or Event of Default or
impair any consequent right.

         SECTION 6.03.     OTHER REMEDIES.

         If an Event of Default occurs and is continuing, the Trustee may pursue
any available remedy to collect the payment of the Issue Price and accrued
Original Issue Discount (or, if the Securities have been converted to Semiannual
Coupon Debentures, the Restated Principal Amount, plus accrued and unpaid
interest) on the Securities or to enforce the performance of any provision of
the Securities or this Indenture.

         The Trustee may maintain a proceeding even if the Trustee does not
possess any of the Securities or does not produce any of the Securities in the
proceeding. A delay or omission by the Trustee or any Holder in exercising any
right or remedy accruing upon an Event of Default

                                       35
<PAGE>   42

shall not impair the right or remedy or constitute a waiver of, or acquiescence
in, the Event of Default. No remedy is exclusive of any other remedy. All
available remedies are cumulative.

         SECTION 6.04.     WAIVER OF PAST DEFAULTS.

         The Holders of a majority in aggregate Principal Amount of the
Securities at the time outstanding, by notice to the Company and the Trustee
(and without notice to any other Holder), may waive an existing Default or Event
of Default and its consequences except (1) an Event of Default described in
Section 6.01(1) or (2) hereof, (2) a Default in respect of a provision that
under Section 9.02 hereof cannot be amended without the consent of each Holder
affected or (3) a Default that constitutes a failure to convert any Security in
accordance with the terms of Article 11 hereof. When a Default or Event of
Default is waived, it is deemed cured, but no such waiver shall extend to any
subsequent or other Default or Event of Default or impair any consequent right.

         SECTION 6.05.     CONTROL BY MAJORITY.

         The Holders of a majority in aggregate Principal Amount of the
Securities at the time outstanding may direct the time, method and place of
conducting any proceeding for any remedy available to the Trustee or of
exercising any trust or power conferred on the Trustee. However, the Trustee may
refuse to follow any direction that conflicts with any law or this Indenture or
that the Trustee determines in good faith is unduly prejudicial to the rights of
other Holders or would involve the Trustee in personal liability unless the
Trustee is offered indemnity reasonably satisfactory to it.

         SECTION 6.06.     LIMITATION ON SUITS.

         A Holder may not pursue any remedy with respect to this Indenture or
the Securities unless:

                  (1) the Holder gives to the Company and the Trustee written
notice stating that an Event of Default is continuing;

                  (2) the Holders of at least 25% in aggregate Principal Amount
of the Securities at the time outstanding make a written request to the Trustee
to pursue the remedy;

                  (3) such Holder or Holders offer to the Trustee reasonable
security or indemnity against any loss, liability or expense satisfactory to the
Trustee;

                  (4) the Trustee does not comply with the request within 60
days after receipt of the notice, the request and the offer of security or
indemnity; and

                  (5) the Holders of a majority in aggregate Principal Amount of
the Securities at the time outstanding do not give the Trustee a direction
inconsistent with the request during such 60 day period.

                                       36
<PAGE>   43

         A Holder may not use this Indenture to prejudice the rights of any
other Holder or to obtain a preference or priority over any other Holder.

         SECTION 6.07.     RIGHTS OF HOLDERS TO RECEIVE PAYMENT.

         Notwithstanding any other provision of this Indenture, the right of any
Holder to receive payment of the Principal Amount, Issue Price, accrued Original
Issue Discount, Redemption Price, Purchase Price, Fundamental Change Purchase
Price, Liquidated Damages, if any, or interest, if any, in respect of the
Securities held by such Holder, on or after the respective due dates expressed
in the Securities or any date of redemption, or to bring suit for the
enforcement of any such payment on or after such respective dates or the right
to convert the Securities in accordance with Article 11, shall not be impaired
or affected adversely without the consent of each such Holder.

         SECTION 6.08.     COLLECTION SUIT BY TRUSTEE.

         If an Event of Default described in Section 6.01(1) or (2) hereof
occurs and is continuing, the Trustee may recover judgment in its own name and
as trustee of an express trust against the Company for the whole amount owing
with respect to the Securities and the amounts provided for in Section 7.07
hereof.

         SECTION 6.09.     TRUSTEE MAY FILE PROOFS OF CLAIM.

         In case of the pendency of any receivership, insolvency, liquidation,
bankruptcy, reorganization, arrangement, adjustment, composition or other
judicial proceeding relative to the Company or any other obligor upon the
Securities or the property of the Company or of such other obligor or their
creditors, the Trustee (irrespective of whether the Principal Amount, Issue
Price, accrued Original Issue Discount, Redemption Price, Purchase Price,
Fundamental Change Purchase Price, Liquidated Damages, if any, or interest, if
any, in respect of the Securities shall then be due and payable as therein
expressed or by declaration or otherwise and irrespective of whether the Trustee
shall have made any demand on the Company for the payment of any such amount)
shall be entitled and empowered, by intervention in such proceeding or
otherwise:

                  (a) to file and prove a claim for the whole amount of the
Principal Amount, Issue Price, accrued Original Issue Discount, Redemption
Price, Purchase Price, Fundamental Change Purchase Price, Liquidated Damages, if
any, or interest, if any, and to file such other papers or documents as may be
necessary or advisable in order to have the claims of the Trustee (including any
claim for the reasonable compensation, expenses, disbursements and advances of
the Trustee, its agents and counsel) and of the Holders allowed in such judicial
proceeding, and

                  (b) to collect and receive any money or other property payable
or deliverable on any such claims and to distribute the same;

and any custodian, receiver, assignee, trustee, liquidator, sequestrator or
similar official in any such judicial proceeding is hereby authorized by each
Holder to make such payments to the Trustee and, in the event that the Trustee
shall consent to the making of such payments directly

                                       37
<PAGE>   44

to the Holders, to pay the Trustee any amount due it for the reasonable
compensation, expenses, disbursements and advances of the Trustee, its agents
and counsel, and any other amounts due the Trustee under Section 7.07 hereof.

         If the Trustee does not file a claim or proof of debt in the form
required in such proceedings prior to 30 days before the expiration of the time
to file such claims or proofs, then any Holder or Holders or their
representative or representatives shall have the right to demand, sue for,
collect, receive and receipt for the payments and distributions in respect of
the Securities which are required to be paid or delivered to the Holders as
provided in this Article and to file and prove all claims therefor and to take
all such other action in the name of the Holders or otherwise as such Holders or
the representative thereof may determine to be necessary or appropriate for the
enforcement of the provisions of this Article.

         Nothing herein contained shall be deemed to authorize the Trustee to
authorize or consent to or accept or adopt on behalf of any Holder any plan of
reorganization, arrangement, adjustment or composition affecting the Securities
or the rights of any Holder thereof, or to authorize the Trustee to vote in
respect of the claims of any Holder in any such proceeding.

         SECTION 6.10.     PRIORITIES.

         If the Trustee collects any money pursuant to this Article 6, it shall
pay out the money in the following order:

         FIRST:  to the Trustee for amounts due under Section 7.07 hereof;

         SECOND: to Holders for amounts due and unpaid on the Securities for the
Principal Amount, Issue Price, accrued Original Issue Discount, Redemption
Price, Purchase Price, Fundamental Change Purchase Price or interest, if any, as
the case may be, ratably, without preference or priority of any kind, according
to such amounts due and payable on the Securities; and

         THIRD:  the balance, if any, to the Company.

         The Trustee may fix a proposed record date and payment date for any
payment to Holders pursuant to this Section 6.10 and shall notify the Company in
writing with respect to such proposed record date and payment date. At least 15
days before such record date, the Company (or the Trustee at the request of the
Company) shall mail to each Holder and the Trustee a notice that states the
record date, the payment date and amount to be paid.

         SECTION 6.11.     UNDERTAKING FOR COSTS.

         In any suit for the enforcement of any right or remedy under this
Indenture or in any suit against the Trustee for any action taken or omitted by
it as Trustee, a court in its discretion may require the filing by any party
litigant (other than the Trustee) in the suit of an undertaking to pay the costs
of the suit, and the court in its discretion may assess reasonable costs,
including reasonable attorneys' fees and expenses, against any party litigant in
the suit, having due regard

                                       38
<PAGE>   45

to the merits and good faith of the claims or defenses made by the party
litigant. This Section 6.11 does not apply to a suit by the Trustee, any suit by
a Holder for the enforcement of the payment of the Principal Amount, accrued
Original Issue Discount, Redemption Price, Purchase Price, Fundamental Change
Purchase Price, Liquidated Damages, if any, or interest, if any, on or after the
due date expressed in such Security or to any suit for the enforcement of the
right to convert the Security pursuant to Article 11, or a suit by Holders of
more than 10% in aggregate Principal Amount of the Securities at the time
outstanding.

         SECTION 6.12.     WAIVER OF STAY, EXTENSION OR USURY LAWS.

         The Company covenants (to the extent that it may lawfully do so) that
it will not at any time insist upon, or plead, or in any manner whatsoever claim
or take the benefit or advantage of, any stay or extension law or any usury or
other law wherever enacted, now or at any time hereafter in force, which would
prohibit or forgive the Company from paying all or any portion of the Principal
Amount, Issue Price, accrued Original Issue Discount, Redemption Price, Purchase
Price or Fundamental Change Purchase Price in respect of Securities, Liquidated
Damages, if any, or any interest on any such amounts, as contemplated herein, or
which may affect the covenants or the performance of this Indenture; and the
Company (to the extent that it may lawfully do so) hereby expressly waives all
benefit or advantage of any such laws and covenants that it will not hinder,
delay or impede the execution of any power herein granted to the Trustee, but
will suffer and permit the execution of every such power as though no such law
had been enacted.

                                   ARTICLE 7.
                                     TRUSTEE

         SECTION 7.01.     DUTIES OF TRUSTEE.

                  (a) If an Event of Default has occurred and is continuing, the
Trustee shall exercise the rights and powers vested in it by this Indenture and
use the same degree of care and skill in its exercise as a prudent man would
exercise or use under the circumstances in the conduct of his own affairs.

                  (b) Except during the continuance of an Event of Default:

                           (1) the Trustee need perform only those duties that
are specifically set forth in this Indenture and no others; and

                           (2) in the absence of bad faith on its part, the
Trustee may conclusively rely, as to the truth of the statements and the
correctness of the opinions expressed therein, upon certificates or opinions
furnished to the Trustee and conforming to the requirements of this Indenture.
However, in the case of any such certificates or opinions which by any provision
hereof are specifically required to be furnished to the Trustee, the Trustee
shall examine the certificates and opinions to determine whether or not they
conform to the requirements of this Indenture.

                                       39
<PAGE>   46

This Section 7.01(b) shall be in lieu of Section 315(a) of the TIA and such
Section 315(a) is hereby expressly excluded from this Indenture, as permitted by
the TIA.

                  (c) The Trustee may not be relieved from liability for its own
negligent action, its own negligent failure to act or its own willful
misconduct, except that:

                           (1) this paragraph (c) does not limit the effect of
paragraph (b) of this Section 7.01;

                           (2) the Trustee shall not be liable for any error of
judgment made in good faith by a Trust Officer unless it is proved that the
Trustee was negligent in ascertaining the pertinent facts; and

                           (3) the Trustee shall not be liable with respect to
any action it takes or omits to take in good faith in accordance with a
direction received by it pursuant to Section 6.05 hereof.

Subparagraphs (c)(1),(2) and (3) shall be in lieu of Sections 315(d)(1),
315(d)(2) and 315(d)(3) of the TIA and such Sections 315(d)(1), 315(d)(2) and
315(d)(3) are hereby expressly excluded from this Indenture, as permitted by the
TIA.

                  (d) Every provision of this Indenture that in any way relates
to the Trustee is subject to paragraphs (a), (b), (c) and (e) of this Section
7.01.

                  (e) The Trustee may refuse to perform any duty or exercise any
right or power or extend or risk its own funds or otherwise incur any financial
liability unless it receives indemnity reasonably satisfactory to it against any
loss, liability or expense.

                  (f) Money held by the Trustee in trust hereunder need not be
segregated from other funds except to the extent required by law.

         SECTION 7.02.     RIGHTS OF TRUSTEE.

         Subject to Section 7.01:

                  (a) The Trustee may conclusively rely on any document
reasonably believed by it to be genuine and to have been signed or presented by
the proper Person. The Trustee need not investigate any fact or matter stated in
the document.

                  (b) Before the Trustee acts or refrains from acting, it may
require a Company Order, an Officers' Certificate or an Opinion of Counsel. The
Trustee shall not be liable for any action it takes or omits to take in good
faith in reliance on a Company Order, Officers' Certificate or Opinion of
Counsel.

                  (c) The Trustee may act through agents and shall not be
responsible for the misconduct or negligence of any agent appointed with due
care.

                                       40
<PAGE>   47

                  (d) The Trustee shall not be liable for any action it takes or
omits to take in good faith which it believes to be authorized or within its
rights or powers.

                  (e) The Trustee may consult with counsel selected by it and
any advice or Opinion of Counsel shall be full and complete authorization and
protection in respect of any action taken or suffered or omitted by it hereunder
in good faith and in accordance with such advice or Opinion of Counsel.

                  (f) The Trustee shall be under no obligation to exercise any
of the rights or powers vested in it by this Indenture, unless the Holders shall
have offered to the Trustee reasonable security or indemnity reasonably
satisfactory to it against the costs, expenses and liabilities which may be
incurred therein or thereby.

                  (g) The Trustee shall not be bound to make any investigation
into the facts or matters stated in any resolution, certificate, statement,
instrument, opinion, report, notice, request, direction, consent, order, bond,
debenture, note, other evidence of indebtedness or other paper or document, but
the Trustee, in its discretion, may make such further inquiry or investigation
into facts or matters as it may see fit, and, if the Trustee shall determine to
make such further inquiry or investigation, it shall be entitled to examine the
books, records and premises of the Company during normal business hours at
reasonable frequencies, personally or by agent or attorney at the sole cost of
the Company and shall incur no liability or additional liability of any kind by
reason of such inquiry or investigation.

                  (h) The Trustee may execute any of the trusts or powers
hereunder or perform any duties hereunder either directly or by or through
agents or attorneys and the Trustee shall not be responsible for any negligent
act on the part of any agent or attorney appointed with due care by it
hereunder.

                  (i) The Trustee shall not be deemed to have notice of any
Default or Event of Default unless a Trust Officer of the Trustee has actual
knowledge thereof or unless written notice of any event which is in fact such a
default is received by the Trustee at the Corporate Trust Office of the Trustee
in accordance with Section 13.02 hereof, and such notice references the
Securities and this Indenture.

                  (j) The rights, privileges, protections, immunities and
benefits given to the Trustee, including, without limitation, its right to be
indemnified, are extended to, and shall be enforceable by, the Trustee in each
of its capacities hereunder, and to each agent, custodian and other Person
employed to act hereunder.

                  (k) The Trustee shall be under no obligation to expend or risk
its own funds or to exercise, at the request or direction of any of the Holders,
any of the rights or powers vested in it by this Indenture pursuant to this
Indenture.

                                       41
<PAGE>   48

         SECTION 7.03.     INDIVIDUAL RIGHTS OF TRUSTEE.

         The Trustee in its individual or any other capacity may become the
owner or pledgee of Securities and may otherwise deal with the Company or its
Affiliates with the same rights it would have if it were not Trustee. Any Paying
Agent, Registrar, Conversion Agent or co-registrar may do the same with the like
rights. However, the Trustee must comply with Sections 7.10 and 7.11 hereof.

         SECTION 7.04.     TRUSTEE'S DISCLAIMER.

         The Trustee makes no representation as to the validity or adequacy of
this Indenture or the Securities; it shall not be accountable for the Company's
use of the proceeds from the Securities; and it shall not be responsible for any
statement in the offering memorandum for the Securities or in this Indenture or
the Securities (other than its certificate of authentication), the acts of a
prior Trustee hereunder, or the determination as to which beneficial owners are
entitled to receive any notices hereunder.

         SECTION 7.05.     NOTICE OF DEFAULTS.

         If a Default occurs and is continuing and if it is actually known by a
Trust Officer or if written notice of any event which is in fact such a default
is received by the Trustee at the Corporate Trust Office of the Trustee in
accordance with Section 13.02 hereof, and such notice references the Securities
and this Indenture, the Trustee shall give to each Holder notice of the Default
within 90 days after it is actually known to a Trust Officer. Except in the case
of a Default described in Section 6.01(1) or (2) hereof, the Trustee may
withhold the notice if and so long as a committee of its Trust Officers in good
faith determines that withholding the notice is in the interests of Holders. The
second sentence of this Section 7.05 shall be in lieu of the proviso to Section
315(b) of the TIA and such provision is hereby expressly excluded from this
Indenture, as permitted by the TIA. The Trustee shall not give notice of a
Default pursuant to Section 6.01(4) until at least 90 days have passed since its
occurrence.

         SECTION 7.06.     REPORTS BY TRUSTEE TO HOLDERS.

         Within 60 days after each May 1, beginning with the May 1 following the
date of this Indenture, the Trustee shall mail to each Holder a brief report
dated as of such May 1 that complies with TIA Section 313(a), if required by
such Section 313(a). The Trustee also shall comply with TIA Section 313(b).

         A copy of each report at the time of its mailing to Holders shall be
filed with the SEC and each securities exchange on which the Securities are
listed. The Company agrees to promptly notify the Trustee whenever the
Securities become listed on any securities exchange and of any delisting
thereof.

         SECTION 7.07.     COMPENSATION AND INDEMNITY.

         The Company agrees:

                                       42
<PAGE>   49

                  (a) to pay to the Trustee from time to time such compensation
as the Company and the Trustee shall from time to time agree in writing for all
services rendered by it hereunder (which compensation shall not be limited by
any provision of law in regard to the compensation of a trustee of an express
trust);

                  (b) to reimburse the Trustee upon its request for all
reasonable expenses, disbursements and advances incurred or made by the Trustee
in accordance with any provision of this Indenture (including the compensation
and the expense, advances and disbursements of its outside agents and counsel),
except any such expense, disbursement or advance as may be attributable to its
negligence or bad faith; and

                  (c) to indemnify the Trustee for, and to hold it harmless
against, any and all loss, damage, claims, liability or expense (including taxes
other than taxes based upon, measured by, or determined by the income of the
Trustee) incurred without negligence or bad faith on its part, arising out of or
in connection with the acceptance or administration of this trust, including the
costs and expenses of defending itself against any claim (whether asserted by
the Company, any Holder or any other Person) or liability in connection with the
exercise or performance of any of its powers or duties hereunder.

         To secure the Company's payment obligations in this Section 7.07, the
Trustee shall have a lien prior to the Securities on all money or property held
or collected by the Trustee, except that held in trust to pay the Principal
Amount, Issue Price, accrued Original Issue Discount, Redemption Price, Purchase
Price, Fundamental Change Purchase Price, Liquidated Damages, if any, or
interest, if any, as the case may be, on particular Securities.

         The Company's payment obligations pursuant to this Section 7.07 shall
survive the discharge of this Indenture. When the Trustee incurs expenses after
the occurrence of a Default specified in Section 6.01(5) or (6), the expenses
are intended to constitute expenses of administration under any Bankruptcy Law.

         SECTION 7.08.     REPLACEMENT OF TRUSTEE.

         The Trustee may resign by so notifying the Company; PROVIDED, HOWEVER,
that no such resignation shall be effective until a successor Trustee has
accepted its appointment pursuant to this Section 7.08. The Holders of a
majority in aggregate Principal Amount of the Securities at the time outstanding
may remove the Trustee by so notifying the Trustee and may appoint a successor
Trustee. The Company shall remove the Trustee if:

                           (1) the Trustee fails to comply with, or ceases to be
         eligible under, Section 7.10 hereof;

                           (2) the Trustee is adjudged bankrupt or insolvent;

                           (3) a receiver or public officer takes charge or
         control of the Trustee or its property or affairs; or

                                       43
<PAGE>   50

                           (4) the Trustee otherwise in the Company's reasonable
         judgment becomes incapable of acting.

         If the Trustee resigns or is removed or if a vacancy exists in the
office of Trustee for any reason, the Company shall promptly appoint, by
resolution of its Board of Directors, a successor Trustee.

         Every successor Trustee appointed hereunder shall execute, acknowledge
and deliver to the Company and to the retiring Trustee an instrument accepting
such appointment, and thereupon the resignation or removal of the retiring
Trustee shall become effective and such successor Trustee, without any further
act, deed or conveyance, shall become vested with all the rights, powers, trusts
and duties of the retiring Trustee; but, on the request of the Company or the
successor Trustee, such retiring Trustee shall, upon payment of its charges,
execute and deliver an instrument transferring to such successor Trustee all the
rights, powers and trusts of the retiring Trustee and shall duly assign,
transfer and deliver to such successor Trustee all property and money held by
such retiring Trustee hereunder, subject to the lien provided for in Section
7.07 hereof. Upon request of any such successor Trustee, the Company shall
execute any and all instruments for more fully and certainly vesting in and
confirming to such successor Trustee all such rights, powers and trusts. No
successor Trustee shall accept its appointment unless at the time of such
acceptance such successor Trustee shall be eligible under this Article.

         If a successor Trustee does not take office within 30 days after the
retiring Trustee resigns or is removed, the retiring Trustee, the Company or the
Holders of a majority in aggregate Principal Amount of the Securities at the
time outstanding may petition any court of competent jurisdiction for the
appointment of a successor Trustee at the expense of the Company.

         If the Trustee fails to comply with Section 7.10 hereof, any Holder may
petition any court of competent jurisdiction for the removal of the Trustee and
the appointment of a successor Trustee.

         SECTION 7.09.     SUCCESSOR TRUSTEE BY MERGER.

         If the Trustee consolidates with, merges or converts into, or transfers
all or substantially all its corporate trust business (including the trust
created by this Indenture) or assets to, another corporation, the resulting,
surviving or transferee corporation without any further act shall be the
successor Trustee hereunder, PROVIDED such corporation shall be otherwise
eligible under this Article, without the execution or filing of any paper or any
further act on the part of any of the parties hereto. As soon as practicable,
the successor Trustee shall give written notice of its succession to the
Company. In case any Securities shall have been authenticated, but not
delivered, by the Trustee then in office, any successor by merger, conversion or
consolidation to such authenticating Trustee may adopt such authentication and
deliver the Securities so authenticated with the same effect as if such
successor Trustee had itself authenticated such Securities.

                                       44
<PAGE>   51

         SECTION 7.10.     ELIGIBILITY; DISQUALIFICATION.

         The Trustee shall at all times satisfy the requirements of TIA Sections
310(a)(1) and 310(b). The Trustee shall have a combined capital and surplus of
at least $50,000,000 (or if the Trustee is a member of a bank holding company
system, its bank holding company shall have a combined capital and surplus of at
least $50,000,000) as set forth in its most recent published annual report of
conditions. Nothing herein contained shall prevent the Trustee from filing with
the SEC the application referred to in the penultimate paragraph of TIA Section
310(b). If at any time the Trustee shall cease to be eligible in accordance with
the provisions of this Section 7.10, it shall correct such ineligibility or
resign immediately in the manner and with the effect specified in this Article
7.

         SECTION 7.11.     PREFERENTIAL COLLECTION OF CLAIMS AGAINST COMPANY.

         The Trustee shall comply with TIA Section 311(a), excluding any
creditor relationship listed in TIA Section 311(b). A Trustee who has resigned
or been removed shall be subject to TIA Section 311(a) to the extent indicated
therein.

                                   ARTICLE 8.
                             DISCHARGE OF INDENTURE

         SECTION 8.01.     DISCHARGE OF LIABILITY ON SECURITIES.

         When (i) the Company delivers to the Trustee all outstanding Securities
(other than Securities replaced pursuant to Section 2.07 hereof) for
cancellation or (ii) all outstanding Securities have become due and payable and
the Company deposits with the Trustee cash and/or securities, as permitted by
the terms hereof, sufficient to pay at Stated Maturity the Principal Amount, or
sufficient to pay at the next Redemption Date the Issue Price plus the
applicable accrued Original Issue Discount to such date, in each case, of all
outstanding Securities (other than Securities replaced pursuant to Section 2.07
hereof), and if in either case the Company pays all other sums payable hereunder
by the Company, then this Indenture shall, subject to Section 7.07 hereof, cease
to be of further effect. The Trustee shall join in the execution of a document
prepared by the Company acknowledging satisfaction and discharge of this
Indenture on demand of the Company accompanied by an Officers' Certificate and
Opinion of Counsel and at the cost and expense of the Company.

         SECTION 8.02.     REPAYMENT TO THE COMPANY.

         The Trustee and the Paying Agent shall return to the Company upon
written request any money or securities held by them for the payment of any
amount with respect to the Securities that remains unclaimed for six months;
PROVIDED, HOWEVER, that the Trustee or such Paying Agent, before being required
to make any such return, shall, in the event that the Securities are no longer
held in global form, at the expense of the Company cause to be published once in
a newspaper of general circulation in The City of New York or mail to each such
Holder notice that such money or securities remains unclaimed and that, after a
date

                                       45
<PAGE>   52

specified therein, which shall not be less than 30 days from the date of such
publication or mailing, any unclaimed money or securities then remaining will be
returned to the Company. After return to the Company, Holders entitled to the
money or securities must look to the Company for payment as general creditors
unless an applicable abandoned property law designates another Person.

                                   ARTICLE 9.
                                   AMENDMENTS

         SECTION 9.01.     WITHOUT CONSENT OF HOLDERS.

         The Company and the Trustee may amend this Indenture and the Securities
without the consent of any Holder:

                           (1) to cure any ambiguity or to correct or supplement
any provision contained herein or in any supplemental indenture which may be
defective or inconsistent with any other provision contained herein or in any
supplemental indenture, or to make any change to any provision contained herein
(including the form of Securities in Exhibit A) necessary or desirable to
accommodate the Company's election under Section 12.01 hereof or the second
paragraph of Section 3.01 hereof, PROVIDED that, in any case, such change shall
not materially adversely affect the interests of the Holders;

                           (2) to provide for the assumption of the Company's
obligations to the Holders of the Securities in case of a merger or
consolidation or conveyance, transfer or lease of the Company's properties and
assets substantially as an entirety;

                           (3) to provide for uncertificated Securities in
addition to or in place of certificated Securities so long as such
uncertificated Securities are in registered form for purposes of the Internal
Revenue Code of 1986, as amended;

                           (4) to make any change that does not adversely affect
the right of any Holder; or

                           (5) to make any change to comply with the TIA, or any
amendment thereto, or to comply with any requirement of the SEC in connection
with the qualification, if any, of the Indenture under the TIA.

         SECTION 9.02.     WITH CONSENT OF HOLDERS.

         The Company and the Trustee, with the written consent of the Holders of
at least a majority in aggregate Principal Amount of the Securities at the time
outstanding, may amend this Indenture or the Securities. However, without the
consent of each Holder affected, an amendment or supplement to this Indenture or
the Securities may not:

                           (1) make any change to the Principal Amount of
Securities whose Holders must consent to an amendment;

                                       46
<PAGE>   53

              (2) make any change to the manner or rate of accrual in connection
with Original Issue Discount, Liquidated Damages, if any, or interest, if any,
reduce the rate of interest referred to in paragraph 1 of the Securities or
extend the time for payment of Original Issue Discount, Liquidated Damages, if
any, or interest, if any, on any Security;

              (3) reduce the Principal Amount or the Issue Price of or extend
the Stated Maturity of any Security (except as provided in Section 12.01);

              (4) reduce the Redemption Price, Purchase Price or Fundamental
Change Purchase Price of any Security;

              (5) make any Security payable in money or securities other than
that stated in the Security;

              (6) [INTENTIONALLY OMITTED];

              (7) make any change in Section 6.04 or 6.07 hereof or this Section
9.02, except to increase the percentage of Holders referenced in Section 6.04 or
6.07 hereof or this Section 9.02, as applicable;

              (8) make any change that adversely affects the right of Holders to
convert any Security; or

              (9) make any change that adversely affects the right of Holders to
require the Company to repurchase the Securities, or the right to require the
Company to repurchase the Securities upon a Fundamental Change, in accordance
with the terms thereof and this Indenture.

         It shall not be necessary for the consent of the Holders under this
Section 9.02 to approve the particular form of any proposed amendment, but it
shall be sufficient if such consent approves the substance thereof.

         After an amendment under this Section 9.02 becomes effective, the
Company shall mail to each Holder a notice briefly describing the amendment.

         SECTION 9.03.  COMPLIANCE WITH TRUST INDENTURE ACT.

         Every supplemental indenture executed pursuant to this Article 9 shall
comply with the TIA as then in effect, if then required to so comply.

         SECTION 9.04.  REVOCATION AND EFFECT OF CONSENTS, WAIVERS AND ACTIONS.

         Until an amendment, waiver or other action becomes effective, a consent
to it or any other action by a Holder of a Security is a continuing consent by
the Holder and every

                                       47
<PAGE>   54

subsequent Holder of that Security or portion of the Security that evidences the
same obligation as the consenting Holder's Security, even if notation of the
consent, waiver or action is not made on the Security. However, any such Holder
or subsequent Holder may revoke the consent, waiver or action as to such
Holder's Security or portion of the Security if the Trustee receives the notice
of revocation before the date the amendment, waiver or action becomes effective.
After an amendment, waiver or action becomes effective, it shall bind every
Holder.

         SECTION 9.05.     NOTATION ON OR EXCHANGE OF SECURITIES.

         Securities authenticated and delivered after the execution of any
supplemental indenture pursuant to this Article 9 may, and shall if required by
the Trustee, bear a notation in form approved by the Trustee as to any matter
provided for in such supplemental indenture. If the Company shall so determine,
new Securities so modified as to conform, in the opinion of the Trustee and the
Board of Directors, to any such supplemental indenture may be prepared and
executed by the Company and authenticated and delivered by the Trustee in
exchange for outstanding Securities.

         SECTION 9.06.     TRUSTEE TO SIGN SUPPLEMENTAL INDENTURES.

         The Trustee shall sign any supplemental indenture authorized pursuant
to this Article 9 if the amendment does not adversely affect the rights, duties,
liabilities or immunities of the Trustee. If it does, the Trustee may, but need
not, sign such supplemental indenture. In signing such amendment the Trustee
shall be entitled to receive, and (subject to the provisions of Section 7.01
hereof) shall be fully protected in relying upon, an Officers' Certificate and
an Opinion of Counsel stating that such amendment is authorized or permitted by
this Indenture.

         SECTION 9.07.     EFFECT OF SUPPLEMENTAL INDENTURES.

         Upon the execution of any supplemental indenture under this Article 9,
this Indenture shall be modified in accordance therewith, and such supplemental
indenture shall form a part of this Indenture for all purposes; and every Holder
of Securities theretofore or thereafter authenticated and delivered hereunder
shall be bound thereby.

                                   ARTICLE 10.
                             [INTENTIONALLY OMITTED]

                                   ARTICLE 11.
                                   CONVERSION

         SECTION 11.01.    CONVERSION PRIVILEGE.

         A Holder of a Security may convert such Security for Common Stock at
any time during the period stated in paragraph 9 of the Securities. The number
of shares of Common Stock issuable upon conversion of a Security per $1,000 of
Principal Amount thereof (the

                                       48
<PAGE>   55

"CONVERSION RATE") shall be that set forth in paragraph 9 in the Securities,
subject to adjustment as herein set forth.

         The Holders' right to convert Securities into shares of Common Stock is
subject to the Company's right to elect to instead pay such Holder the amount of
cash set forth in the next succeeding sentence, in lieu of delivering such
shares of Common Stock; PROVIDED, HOWEVER, that (x) if such payment of cash is
not permitted pursuant to the provisions of this Indenture or the provisions of
any other agreement or instrument to which the Company is a party or by which it
is bound or otherwise or (y) if an Event of Default (other than a default in a
cash payment upon conversion of the Securities) shall have occurred and be
continuing, the Company shall deliver shares of Common Stock (and cash in lieu
of fractional shares of Common Stock) in accordance with this Article 11,
whether or not the Company has delivered a notice pursuant to Section 11.02
hereof to the effect that the Securities would be paid in cash. The amount of
cash to be paid pursuant to Section 11.02 hereof for each $1,000 of Principal
Amount of a Security upon conversion shall be equal to the Sale Price of the
Common Stock on the Trading Day immediately prior to the related Conversion Date
multiplied by the Conversion Rate in effect on such Trading Day. The Company
shall not pay cash in lieu of delivering shares of Common Stock upon the
conversion of any Security pursuant to the terms of this Article 11 (other than
cash in lieu of fractional shares pursuant to Section 11.03 hereof) if there has
occurred (prior to, on or after, as the case may be, the Conversion Date or the
date on which the Company delivers its notice of whether such Security shall be
converted into shares of Common Stock or cash pursuant to Section 11.02 hereof)
and is continuing an Event of Default (other than a default in a cash payment
upon conversion of such Securities), PROVIDED, HOWEVER, that this sentence shall
not apply in the event that an Event of Default occurs after such cash is paid.

         A Holder may convert a portion of the Principal Amount of a Security if
the portion is $1,000 or an integral multiple of $1,000. Provisions of this
Indenture that apply to conversion of all of a Security also apply to conversion
of a portion of a Security.

         SECTION 11.02.    CONVERSION PROCEDURE.

         To convert a Security a Holder must satisfy the requirements in
paragraph 9 of the Securities. The date on which the Holder of Securities
satisfies all those requirements is the conversion date (the "CONVERSION DATE").
The Company shall use reasonable efforts to deliver, on the same Business Day as
its receipt of a conversion notice from the Conversion Agent (but, in any event
within one Business Day following the receipt of a conversion notice from the
Conversion Agent), to the Conversion Agent for delivery to the Holders written
notice of whether such Security shall be converted into shares of Common Stock
or paid in cash. If the Company shall have notified the Conversion Agent that
all or a portion of such Security shall be converted into shares of Common
Stock, the Company shall deliver to the Holder no later than the seventh
Business Day following the Conversion Date a certificate for the number of full
shares of Common Stock issuable upon the conversion and cash in lieu of any
fractional share determined pursuant to Section 11.03 hereof. Except as provided
in Section 11.01 hereof, if the Company shall have notified the Holder that all
or a portion of such Security shall be paid in cash, the Company shall deliver
to the Holder surrendering such Security the amount of cash payable with respect
to such Security on the tenth Business Day following such Conversion

                                       49
<PAGE>   56

Date. Except as provided in Section 11.01 hereof, the Company may not change its
election with respect to the consideration to be delivered upon conversion of a
Security once the Company has notified the Holder in accordance with this
paragraph. The Person in whose name the certificate is registered shall be
treated as the stockholder of record on and after the Conversion Date; PROVIDED,
HOWEVER, that no surrender of a Security on any date when the stock transfer
books of the Company shall be closed shall be effective to constitute the Person
or Persons entitled to receive the shares of Common Stock upon such conversion
as the record holder or holders of such shares of Common Stock on such date, but
such surrender shall be effective to constitute the Person or Persons entitled
to receive such shares of Common Stock as the record holder or holders thereof
for all purposes at the close of business on the next succeeding day on which
such stock transfer books are open; such conversion shall be at the Conversion
Rate in effect on the date that such Security shall have been surrendered for
conversion, as if the stock transfer books of the Company had not been closed.
Upon conversion of a Security, such Person shall no longer be a Holder of such
Security.

         No payment on the Securities or adjustment of the Conversion Rate will
be made for dividends on or other distributions with respect to any Common Stock
except as provided in this Article 11. On conversion of a Security, that portion
of accrued Original Issue Discount (or interest, if the Company has exercised
the option provided for in Section 12.01 hereof) attributable to the period from
the Issue Date (or, if the Company has exercised the option provided for in
Section 12.01 hereof, the later of (x) the date of such exercise and (y) the
date on which interest was last paid) to the Conversion Date with respect to the
converted Security shall not be canceled, extinguished or forfeited, but rather
shall be deemed to be paid in full to the Holder thereof through delivery of the
Common Stock (together with the cash payment, if any, in lieu of fractional
shares) in exchange for the Security being converted pursuant to the provisions
hereof.

         If a Holder converts more than one Security at the same time, the
number of shares of Common Stock issuable or cash paid upon the conversion shall
be based on the total Principal Amount of the Securities converted.

         Upon surrender of a Security that is converted in part, the Company
shall execute, and the Trustee shall authenticate and deliver to the Holder, a
new Security in an authorized denomination equal in Principal Amount to the
unconverted portion of the Security surrendered.

         If the last day on which a Security may be converted is a Legal Holiday
in a place where a Conversion Agent is located, the Security may be surrendered
to that Conversion Agent on the next succeeding day that it is not a Legal
Holiday.

         SECTION 11.03.    FRACTIONAL SHARES.

         The Company will not issue a fractional share of Common Stock upon
conversion of a Security. Instead the Company will deliver cash for the current
market value of the fractional share. The current market value of a fractional
share shall be determined to the nearest 1/10,000th of a share by multiplying
the last reported sale price (determined as set forth in the

                                       50
<PAGE>   57

definition of Market Price) on the last Trading Day prior to the Conversion Date
of a full share by the fractional amount and rounding the product to the nearest
whole cent.

         SECTION 11.04.    TAXES ON CONVERSION.

         If a Holder converts a Security, the Company shall pay any documentary,
stamp or similar issue or transfer tax due on the issue of shares of Common
Stock upon the conversion. However, the Holder shall pay any such tax which is
due because the Holder requests the shares to be issued in a name other than the
Holder's name. The Conversion Agent may refuse to deliver the certificates
representing the Common Stock being issued in a name other than the Holder's
name until the Conversion Agent receives a sum sufficient to pay any tax which
will be due because the shares are to be issued in a name other than the
Holder's name. Nothing herein shall preclude any tax withholding required by law
or regulations.

         SECTION 11.05.    COMPANY TO PROVIDE STOCK.

         The Company shall, prior to issuance of any Securities hereunder, and
from time to time as may be necessary, reserve out of its authorized but
unissued Common Stock a sufficient number of shares of Common Stock to permit
the conversion of the Securities. The shares of Common Stock or other securities
issued upon conversion of the Securities shall bear any legend required by
Section 2.06(d) hereof.

         All shares of Common Stock delivered upon conversion of the Securities
shall be newly issued shares or treasury shares, shall be duly and validly
issued and fully paid and nonassessable and shall be free from preemptive rights
and free of any lien or adverse claim.

         The Company covenants that if any shares of Common Stock to be provided
for the purpose of conversion of Securities hereunder require registration with
or approval of any governmental authority under any federal or state law before
such shares may be validly issued upon conversion, the Company will in good
faith and as expeditiously as possible endeavor to secure such registration or
approval, as the case may be.

         The Company further covenants that if at any time the Common Stock
shall be quoted or listed on the NASDAQ National Market or the AMEX or any other
automated quotation system or national securities exchange, the Company will, if
permitted by the rules of such automated quotation system or exchange, list and
keep listed, so long as the Common Stock shall be so listed on such automated
quotation system or exchange, all shares of Common Stock issuable upon
conversion of the Securities; PROVIDED, HOWEVER, that if the rules of such
automated quotation system or exchange permit the Company to defer the listing
of such Common Stock until the first conversion of the Securities into Common
Stock in accordance with the provisions of this Indenture, the Company covenants
to list such Common Stock issuable upon conversion of the Securities in
accordance with the requirements of such automated quotation system or exchange
at such time.

                                       51
<PAGE>   58
         SECTION 11.06.    ADJUSTMENT FOR CHANGE IN CAPITAL STOCK.

         In case the Company shall (i) pay a dividend, or make a distribution,
in shares of its Common Stock, on its Common Stock, (ii) subdivide its
outstanding Common Stock into a greater number of shares, or (iii) combine its
outstanding Common Stock into a smaller number of shares, the Conversion Rate in
effect immediately prior thereto shall be adjusted so that the Holder of any
Security thereafter surrendered for conversion shall be entitled to receive the
number of shares of Common Stock which such Holder would have owned or have been
entitled to receive after the occurrence of any of the events described above
had such Security been converted immediately prior to the occurrence of such
event. If any dividend or distribution of the type described in clause (i) above
is not so paid or made, the Conversion Rate shall again be adjusted to the
Conversion Rate which would then be in effect if such dividend as distribution
had not been declared. An adjustment made pursuant to this Section 11.06 shall
become effective immediately after the record date in the case of a dividend and
shall become effective immediately after the effective date in the case of a
subdivision or combination.

         SECTION 11.07.    ADJUSTMENT FOR RIGHTS OR WARRANTS.

         In case the Company shall issue rights or warrants to all holders of
its Common Stock entitling them (for a period expiring within 45 days after the
record date mentioned below) to subscribe for or purchase Common Stock at a
price per share less than the Market Price per share of Common Stock at the
record date for the determination of stockholders entitled to receive such
rights or warrants, the Conversion Rate in effect immediately prior thereto
shall be adjusted so that the same shall equal the Conversion Rate determined by
multiplying the Conversion Rate in effect immediately prior to the date of
issuance of such rights or warrants by a fraction of which the numerator shall
be the number of shares of Common Stock outstanding on the date of issuance of
such rights or warrants plus the number of additional shares of Common Stock
offered to holders of Common Stock for subscription or purchase, and of which
the denominator shall be the number of shares of Common Stock outstanding on the
date of issuance of such rights or warrants plus the number of shares of Common
Stock which the aggregate offering price of the total number of shares so
offered would purchase at such Market Price. Such adjustment shall be made
successively whenever any such rights or warrants are issued, and shall become
effective immediately after the opening of business on the day following the
record date for the determination of the stockholders entitled to receive such
rights or warrants. To the extent that shares of Common Stock are not delivered
after the expiration of such rights or warrants, the Conversion Rate shall be
readjusted to the Conversion Rate which would then be in effect had the
adjustments made upon the issuance of such rights or warrants been made on the
basis of delivery of only the number of shares of Common Stock actually
delivered. If such rights or warrants are not so issued, the Conversion Rate
shall again be adjusted to be the Conversion Rate which would then be in effect
if such record date for the determination of stockholders entitled to receive
such rights or warrants had not been fixed. In determining whether any rights or
warrants entitle the holders to subscribe for or purchase shares of Common Stock
at less than such Market Price of such Common Stock, and in determining the
aggregate offering price of such shares of Common Stock, there shall be taken
into account any consideration received by the Company for such rights or
warrants, the value of such consideration, if other than cash, to be determined
by the Board of Directors.

                                       52
<PAGE>   59

         SECTION 11.08.    ADJUSTMENT FOR OTHER DISTRIBUTIONS.

                  (a) In case the Company shall distribute to all holders of its
Common Stock (excluding any distribution in connection with the liquidation,
dissolution or winding up of the Company, whether voluntary or involuntary) any
shares of any class of capital stock of the Company (other than Common Stock),
or evidences of indebtedness of the Company or of assets (other than cash and
other than dividends, distributions or rights or warrants to subscribe for or
purchase any of its securities referred to in Section 11.07 hereof) (any of the
foregoing hereinafter in this Section 11.08(a) called the "DISTRIBUTED
SECURITIES"), then, the Conversion Rate shall be adjusted so that the same shall
equal the Conversion Rate determined by multiplying the Conversion Rate in
effect immediately prior to the date of such distribution by a fraction of which
the numerator shall be the Market Price per share of the Common Stock on the
record date mentioned below, and the denominator shall be the Market Price per
share of the Common Stock on such record date less the fair market value on such
record date (as determined by the Board of Directors, whose determination shall
be conclusive, and described in a certificate filed with the Trustee) of the
Distributed Securities so distributed applicable to one share of Common Stock.
Such adjustment shall become effective immediately after the record date for the
determination of stockholders entitled to receive such distribution.
Notwithstanding the foregoing, in the event that the then fair market value (as
so determined) of the portion of the Distributed Securities so distributed
applicable to one share of Common Stock is equal to or greater than the Market
Price of the Common Stock on the record date, in lieu of the foregoing
adjustment, adequate provision shall be made so that each Holder shall have the
right to receive upon conversion the amount of Distributed Securities such
Holder would have received had such Holder converted each Security immediately
prior to such record date. In the event that such distribution is not so paid or
made, the Conversion Rate shall again be adjusted to the Conversion Rate which
would then be in effect if such distribution had not been declared. If the Board
of Directors determines the fair market value of any distribution for purposes
of this Section 11.08(a) by reference to the actual or when issued trading
market for any securities, it must in doing so consider the prices in such
market over the same period used in computing the Market Price of the Common
Stock.

         Notwithstanding the foregoing provisions of this Section 11.08(a), no
adjustment shall be made thereunder for any distribution of Distributed
Securities if the Company makes proper provision so that each Holder of a
Security who converts such Security (or any portion thereof) after the record
date for such distribution shall be entitled to receive upon such conversion, in
addition to the shares of Common Stock issuable upon such conversion, the amount
and kind of Distributed Securities that such Holder would have been entitled to
receive if such Holder had, immediately prior to such record date, converted
such Security for Common Stock; PROVIDED that, with respect to any Distributed
Securities that are convertible, exchangeable or exercisable, the foregoing
provision shall only apply to the extent (and so long as) the Distributed
Securities receivable upon conversion of such Security would be convertible,
exchangeable or exercisable, as applicable, without any loss of rights or
privileges for a period of at least 60 days following conversion of such
Security.

                                       53
<PAGE>   60

                  (b) In case the Company shall, by dividend or otherwise,
distribute to all holders of its Common Stock cash (excluding (x) any quarterly
cash dividend on the Common Stock to the extent the aggregate cash dividend per
share of Common Stock in any fiscal quarter does not exceed the greater of (A)
the amount per share of Common Stock of the immediately preceding quarterly cash
dividend on the Common Stock to the extent such preceding quarterly dividend did
not require any adjustment of the Conversion Rate pursuant to this Section
11.08(b) (as adjusted to reflect subdivisions or combinations of the Common
Stock), and (B) 4.5% of the average of the last reported sales price of the
Common Stock (determined as provided in the definition of Market Price) during
the ten Trading Days immediately prior to the date of declaration of such
dividend and (y) any dividend or distribution in connection with the
liquidation, dissolution or winding up of the Company, whether voluntary or
involuntary), then, in such case, unless the Company elects to reserve such cash
for distribution to the Holders of the Securities upon the conversion of the
Securities so that any such Holder converting Securities will receive upon such
conversion in addition to the shares of Common Stock to which such Holder is
entitled, the amount of cash which such Holder would have received if such
Holder had, immediately prior to the record date for such distribution of cash,
converted its Securities for Common Stock, the Conversion Rate shall be
increased so that the same shall equal the Conversion Rate determined by
multiplying the Conversion Rate in effect immediately prior to the record date
by a fraction of which the numerator shall be such Market Price of the Common
Stock and the denominator shall be the Market Price of the Common Stock on the
record date less the amount of cash so distributed (and not excluded as provided
above) applicable to one share of Common Stock, such increase to be effective
immediately prior to the opening of business on the day following the record
date; PROVIDED, HOWEVER, that in the event that the portion of the cash so
distributed applicable to one share of Common Stock is equal to or greater than
the Market Price of the Common Stock on the record date, in lieu of the
foregoing adjustment, adequate provision shall be made so that each Holder shall
have the right to receive upon conversion the amount of cash such Holder would
have received had such Holder converted each Security on the record date. If
such dividend or distribution is not so paid or made, the Conversion Rate shall
again be adjusted to be the Conversion Rate which would then be in effect if
such dividend or distribution had not been declared. If any adjustment is
required to be made as set forth in this Section 11.08(b) as a result of a
distribution that is a quarterly dividend, such adjustment shall be based upon
the amount by which such distribution exceeds the amount of the quarterly cash
dividend permitted to be excluded pursuant hereto. If an adjustment is required
to be made as set forth in this Section 11.08(b) above as a result of a
distribution that is not a quarterly dividend, such adjustment shall be based
upon the full amount of the distribution.

         SECTION 11.09.    WHEN ADJUSTMENT MAY BE DEFERRED.

         No adjustment in the Conversion Rate need be made unless the adjustment
would require an increase or decrease of at least 1% in the Conversion Rate. Any
adjustments that are made shall be carried forward and taken into account any
subsequent adjustment.

         All calculations under this Article 11 shall be made to the nearest
cent or to the nearest 1/10,000th of a share, as the case may be.

                                       54
<PAGE>   61

         SECTION 11.10.    WHEN NO ADJUSTMENT REQUIRED.

         No adjustment need be made for rights to purchase Common Stock pursuant
to a Company plan for reinvestment of dividends or interest.

         No adjustment need be made for a change in the par value or no par
value of the Common Stock.

         To the extent the Securities become convertible into cash, assets,
property or securities (other than capital stock of the Company), no adjustment
need be made thereafter as to the cash, assets, property or such securities.
Interest will not accrue on the cash.

         SECTION 11.11.    NOTICE OF ADJUSTMENT.

         Whenever the Conversion Rate is adjusted, the Company shall promptly
mail to Holders a notice of the adjustment. The Company shall file with the
Trustee and the Conversion Agent such notice. The certificate shall, absent
manifest error, be conclusive evidence that the adjustment is correct. Neither
the Trustee nor any Conversion Agent shall be under any duty or responsibility
with respect to any such certificate except to exhibit the same to any Holder
desiring inspection thereof.

         SECTION 11.12.    VOLUNTARY CHANGE.

         The Company may make such increases or decreases, in one or more
increments, in the Conversion Rate, in addition to those required by Sections
11.06, 11.07 and 11.08 hereof, as the Board of Directors considers to be
advisable to avoid or diminish any income tax to holders of Common Stock or
rights to purchase Common Stock resulting from any dividend or distribution of
stock (or rights to acquire stock) or from any event treated as such for income
tax purposes. To the extent permitted by applicable law, the Company may from
time to time increase, in one or more increments, the Conversion Rate by any
amount for any period of time if the period is at least 20 Business Days, the
increase is irrevocable during the period and the Board of Directors shall have
made a determination that such increase would be in the best interests of the
Company, which determination shall be conclusive. Subsequent to any such
increase, the Company may from time to time lower the Conversion Rate to any
rate that is not lower than the Conversion Rate that would have been applicable
had any such increase not occurred, if the Board of Directors has determined
that the decrease would be in the Company's best interests. Whenever the
Conversion Rate is changed pursuant to this Section 11.12, the Company shall
mail to Holders and file with the Trustee and the Conversion Agent a notice of
such increase. The Company shall mail such notice at least seven days before the
date the increased or decreased Conversion Rate takes effect. The notice shall
state the increased or decreased Conversion Rate and the period it will be in
effect.

         SECTION 11.13.    NOTICE OF CERTAIN TRANSACTIONS.

         If:

                                       55
<PAGE>   62

                           (1) the Company makes any distribution or dividend
                  that would require an adjustment in the Conversion Rate
                  pursuant to Section 11.06, 11.07 or 11.08 hereof; or

                           (2) the Company takes any action that would require a
                  supplemental indenture pursuant to Section 11.14 hereof; or

                           (3) there is a liquidation, dissolution or winding-up
                  of the Company;

then the Company shall mail to Holders and file with the Trustee and the
Conversion Agent a notice stating the proposed record date for a dividend or
distribution or the proposed effective date of a subdivision, combination,
reclassification, consolidation, merger, conveyance , transfer, lease,
dissolution, liquidation or winding-up. The Company shall file and mail the
notice at least 10 days before such date. Failure to file or mail the notice or
any defect in it shall not affect the validity of the transaction.

         SECTION 11.14. EFFECT OF RECLASSIFICATION, CONSOLIDATION, MERGER OR
TRANSFER.

         If any of the following events occur, namely (i) any reclassification
or change of outstanding shares of Common Stock (other than a change in par
value, or from par value to no par value, or from no par value to par value, or
as a result of a subdivision or combination), (ii) any consolidation, merger or
combination of the Company with one or more other Persons as a result of which
holders of Common Stock shall be entitled to receive stock, securities or other
property or assets (including cash) with respect to or in exchange for such
Common Stock, or (iii) any conveyance, transfer or lease of the properties and
assets of the Company substantially as an entirety to any other Person as a
result of which holders of Common Stock shall be entitled to receive stock,
securities or other property or assets (including cash) with respect to or in
exchange for such Common Stock, then the Company or the successor or purchasing
Person, as the case may be, shall execute with the Trustee a supplemental
indenture, providing that each Security shall be convertible into the kind and
amount of shares of stock and other securities or property or assets (including
cash) receivable upon such reclassification, change, consolidation, merger,
combination, conveyance, transfer or lease by a holder of a number of shares of
Common Stock issuable upon conversion of such Securities immediately prior to
such reclassification, change, consolidation, merger, combination, conveyance,
transfer or lease. Such supplemental indenture shall provide for adjustments
which shall be as nearly equivalent as may be practicable to the adjustments
provided for in this Article.

         The Company shall cause notice of the execution of such supplemental
indenture to be mailed to each Holder of Securities, at such Holder's address
appearing on the Security register provided for in Section 2.03 hereof.

         The above provisions of this Section shall similarly apply to
successive reclassifications, changes, consolidations, mergers, combinations,
conveyances, transfers or leases.

         If this Section applies, none of Sections 11.06, 11.07 nor 11.08 hereof
apply.

                                       56
<PAGE>   63

         SECTION 11.15.  COMPANY DETERMINATION FINAL.

         Any determination that the Company or the Board of Directors must make
pursuant to Section 11.03, 11.06, 11.07, 11.08, 11.09, 11.10, 11.12, 11.14 or
11.17 hereof shall be conclusive in the absence of manifest error.

         SECTION 11.16.  TRUSTEE'S ADJUSTMENT DISCLAIMER.

         The Trustee has no duty to determine when an adjustment under this
Article 11 should be made, how it should be made or what it should be. The
Trustee has no duty to determine whether a supplemental indenture under Section
11.14 hereof need be entered into or whether any provisions of any supplemental
indenture are correct. The Trustee shall not be accountable for and makes no
representation as to the validity or value of any securities or assets issued
upon conversion of Securities. The Trustee shall not be responsible for the
Company's failure to comply with this Article 11, and shall not be deemed to
have knowledge of any adjustment unless and until it shall have received a
notice of adjustment pursuant to Section 11.11 hereof. Each Conversion Agent
(other than the Company or one of its Affiliates) shall have the same protection
under this Section 11.16 as the Trustee.

         SECTION 11.17.  SIMULTANEOUS ADJUSTMENTS.

         In the event that this Article 11 requires adjustments to the
Conversion Rate under more than one of Section 11.06, 11.07, 11.08(a) or
11.08(b) hereof, and the record dates for the distributions giving rise to such
adjustments shall occur on the same date, then such adjustments shall be made by
applying, first, the provisions of Section 11.08(a) hereof, second, the
provisions of Section 11.08(b) hereof, third, the provisions of Section 11.06
hereof and, fourth, the provisions of Section 11.07 hereof, PROVIDED that no
adjustment shall be made more than once pursuant to any such individual Section.

         SECTION 11.18.  SUCCESSIVE ADJUSTMENTS.

         After an adjustment to the Conversion Rate under this Article 11, any
subsequent event requiring an adjustment under this Article 11 shall cause an
adjustment to the Conversion Rate as so adjusted.

         SECTION 11.19.  RIGHTS ISSUED IN RESPECT OF COMMON STOCK ISSUED UPON
         CONVERSION.

         Notwithstanding any other provision hereof, in the event that the
Company implements a stockholders' rights plan, such rights plan shall provide
that upon conversion of the Securities the Holders will receive, in addition to
the Common Stock issuable upon such conversion, such rights, whether or not such
rights have separated from the Common Stock at the time of such conversion.

                                       57
<PAGE>   64

         Rights or warrants distributed by the Company to all holders of Common
Stock entitling the holders thereof to subscribe for or purchase shares of the
Company's capital stock (either initially or under certain circumstances), which
rights or warrants, until the occurrence of a specified event or events
("TRIGGER EVENT"):

         (i)     are deemed to be transferred with such shares of Common Stock,

         (ii)    are not exercisable, and

         (iii)   are also issued in respect of future issuances of Common Stock,

shall not be deemed distributed for purposes of Section 11.08(a) hereof until
the occurrence of the earliest Trigger Event. In addition, in the event of any
distribution of rights or warrants, or any Trigger Event with respect thereto,
that shall have resulted in an adjustment to the Conversion Rate under Section
11.08(a) hereof, (1) in the case of any such rights or warrants which shall all
have been redeemed or repurchased without exercise by any holders thereof, the
Conversion Rate shall be readjusted upon such final redemption or repurchase to
give effect to such distribution or Trigger Event, as the case may be, as though
it were a cash distribution, equal to the per share redemption or repurchase
price received by a holder of Common Stock with respect to such rights or
warrants (assuming such holder had retained such rights or warrants), made to
all holders of Common Stock as of the date of such redemption or repurchase, and
(2) in the case of any such rights or warrants all of which shall have expired
without exercise by any holder thereof, the Conversion Rate shall be readjusted
as if such issuance had not occurred.

         SECTION 11.20. GENERAL CONSIDERATIONS.

         Whenever successive adjustments to the Conversion Rate are called for
pursuant to this Article 11, such adjustments shall be made to the Market Price
as may be necessary or appropriate to effectuate the intent of this Article 11
and to avoid unjust or inequitable results as determined in good faith by the
Board of Directors.

                                   ARTICLE 12.
                                SPECIAL TAX EVENT

         SECTION 12.01. OPTIONAL CONVERSION TO SEMIANNUAL COUPON DEBENTURE UPON
TAX EVENT.

         From and after the date (the "TAX EVENT DATE") of the occurrence of a
Tax Event, at the option of the Company, interest in lieu of future Original
Issue Discount shall accrue at 2.5% per annum on a principal amount per Security
(the "RESTATED PRINCIPAL AMOUNT") equal to the Issue Price plus Original Issue
Discount accrued to the date immediately prior to the Tax Event Date or the date
on which the Company exercises the option described herein (to convert the
Security into a Semiannual Coupon Debenture (the "SEMIANNUAL COUPON
DEBENTURE")), whichever is later (such date, the "OPTION EXERCISE DATE"). Such
interest shall accrue from the Option Exercise Date and shall be payable
semiannually on

                                       58
<PAGE>   65

February 5 and August 5 of each year (each an "INTEREST PAYMENT DATE") to
Holders of record at the close of business on January 15 or July 15 (each a
"REGULAR RECORD DATE") immediately preceding such Interest Payment Date.
Interest will be computed on the basis of a 360-day year comprised of twelve
30-day months and will accrue from the most recent date on which interest has
been paid or, if no interest has been paid, from the Option Exercise Date.
Within 15 days of the occurrence of a Tax Event, the Company shall mail a
written notice of such Tax Event by first-class mail to the Trustee, and the
Trustee or the Custodian, at the direction of the Trustee, shall make any
necessary endorsement of each Security in global form then outstanding so that
it reflects the Restated Principal Amount.

         SECTION 12.02.    PAYMENT OF INTEREST; INTEREST RIGHTS PRESERVED.

                  (a) Interest on any Security that is payable, and is
punctually paid or duly provided for, on any Interest Payment Date shall be paid
to the Person in whose name that Security is registered at the close of business
on the Regular Record Date for such interest at the office or agency of the
Company maintained for such purpose. Each installment of interest on any
Security shall be paid in same-day funds by transfer to an account maintained by
the payee located inside the United States. In the case of a permanent global
Security, interest payable on any Interest Payment Date will be paid to the
Depositary, Euroclear and/or Clearstream, as the case may be, with respect to
that portion of such permanent global Security held for its account by Cede &
Co. or the London office of a depositary, as the case may be, for the purpose of
permitting such party to credit the interest received by it in respect of such
permanent global Security to the accounts of the beneficial owners thereof.

                  (b) Except as otherwise specified with respect to the
Securities, any interest on any Security that is payable, but is not punctually
paid or duly provided for, within 30 days following any Interest Payment Date
(herein called "DEFAULTED INTEREST") shall forthwith cease to be payable to the
registered Holder thereof on the relevant Regular Record Date by virtue of
having been such Holder, and such Defaulted Interest may be paid by the Company,
as its election in each case, as provided in clause (1) or (2) below:

                           (1) The Company may elect to make payment of any
                  Defaulted Interest to the persons in whose names the
                  Securities are registered at the close of business on a
                  special record date (herein called "SPECIAL RECORD DATE") for
                  the payment of such Defaulted Interest, which shall be fixed
                  in the following manner. The Company shall notify the Trustee
                  in writing of the amount of Defaulted Interest proposed to be
                  paid on each Security and the date of the proposed payment
                  (which shall not be less than 20 days after such notice is
                  received by the Trustee), and at the same time the Company
                  shall deposit with the Trustee an amount of money equal to the
                  aggregate amount proposed to be paid in respect of such
                  Defaulted Interest or shall make arrangements satisfactory to
                  the Trustee for such deposit on or prior to the date of
                  proposed payment, such money when deposited to be held in
                  trust for the benefit of the persons entitled to such
                  Defaulted Interest as in this clause provided. Thereupon the
                  Trustee shall fix a Special Record Date for the payment of
                  such Defaulted Interest which shall be not more than 15 days
                  and not less than 10 days prior to the date of the proposed

                                       59
<PAGE>   66

                  payment and not less than 10 days after the receipt by the
                  Trustee of the notice of the proposed payment. The Trustee
                  shall promptly notify the Company of such Special Record Date
                  and, in the name and at the expense of the Company, shall
                  cause notice of the proposed payment of such Defaulted
                  Interest and the Special Record Date therefor to be mailed,
                  first-class postage prepaid, to each Holder of Securities at
                  his address as it appears on the list of Holders maintained
                  pursuant to Section 2.05 hereof not less than 10 days prior to
                  such Special Record Date. The Trustee may, in its discretion,
                  in the name and at the expense of the Company, cause a similar
                  notice to be published at least once in an Authorized
                  Newspaper in each place of payment, but such publications
                  shall not be a condition precedent to the establishment of
                  such Special Record Date. Notice of the proposed payment of
                  such Defaulted Interest and the Special Record Date therefor
                  having been mailed as aforesaid, such Defaulted Interest shall
                  be paid to the persons in whose names the Securities are
                  registered at the close of business on such Special Record
                  Date and shall no longer be payable pursuant to the following
                  clause (2).

                           (2) The Company may make payment of any Defaulted
                  Interest on the Securities in any other lawful manner not
                  inconsistent with the requirements of any securities exchange
                  on which such Securities may be listed, and upon such notice
                  as may be required by such exchange, if, after notice given by
                  the Company to the Trustee of the proposed payment pursuant to
                  this clause, such manner of payment shall be deemed
                  practicable by the Trustee.

         Subject to the foregoing provisions of this Section and Section 2.06
hereof, each Security delivered under this Indenture upon registration of
transfer of or in exchange for or in lieu of any other Security shall carry the
rights to interest accrued and unpaid, and to accrue, which were carried by such
other Security.

                                   ARTICLE 13.
                                  MISCELLANEOUS

         SECTION 13.01.    TRUST INDENTURE ACT.

         This Indenture is hereby made subject to, and shall be governed by, the
provisions of the TIA required to be part of and to govern indentures qualified
under the TIA; PROVIDED, HOWEVER that this Section 13.01 shall not require this
Indenture or the Trustee to be qualified under the TIA prior to the time such
qualification is in fact required under the terms of the TIA, nor shall it
constitute any admission or acknowledgment by either party that any such
qualification is required prior to the time such qualification is in fact
required under the terms of the TIA. If any provision hereof limits, qualifies
or conflicts with another provision hereof which is required to be included in
an indenture qualified under the TIA, such required provision shall control.

                                       60
<PAGE>   67

         SECTION 13.02.    NOTICES.

         Any request, demand, authorization, notice, waiver, consent or
communication shall be in writing in the English language and delivered in
Person or mailed by first class mail, postage prepaid, addressed as follows or
transmitted by facsimile transmission (confirmed by overnight courier) to the
following facsimile numbers:

         if to the Company:

                  Nabors Industries, Inc.
                  515 West Greens Road, Suite 1200
                  Houston, Texas  77067
                  Attn:  President
                  (with a copy to its Legal Department)
                  Telephone Number:  (281) 874-0035
                  Facsimile Number:  (281) 775-8431

         if to the Trustee:

                  Bank One, N.A.
                  100 East Broad Street, 8th Floor
                  Columbus, Ohio  43215
                  Attn:  Global Corporate Trust Services Group
                  Telephone Number:  (614) 248-6229
                  Facsimile Number:  (614) 248-5195

         The Company or the Trustee by notice to the other may designate
additional or different addresses for subsequent notices or communications.

         Any notice or communication given to a Holder shall be mailed to the
Holder, by first class mail, postage prepaid, at the Holder's address as it
appears on the registration books of the Registrar and shall be sufficiently
given if so mailed within the time prescribed.

         Failure to mail a notice or communication to a Holder or any defect in
it shall not affect its sufficiency with respect to other Holders. If a notice
or communication is mailed in the manner provided above, it is duly given,
whether or not received by the addressee.

         If the Company mails a notice or communication to the Holders, it shall
mail a copy to the Trustee and each Registrar, Paying Agent, Conversion Agent or
co-registrar.

         SECTION 13.03.    COMMUNICATION BY HOLDERS WITH OTHER HOLDERS.

         Holders may communicate pursuant to TIA Section 312(b) with other
Holders with respect to their rights under this Indenture or the Securities. The
Company, the Trustee, the Registrar, the Paying Agent, the Conversion Agent and
anyone else shall have the protection of TIA Section 312(c).

                                       61
<PAGE>   68

         SECTION 13.04.    CERTIFICATE AND OPINION AS TO CONDITIONS PRECEDENT.

         Upon any request or application by the Company to the Trustee to take
any action under this Indenture, the Company shall furnish to the Trustee:

                  (1) an Officers' Certificate stating that, in the opinion of
the signers, all conditions precedent, if any, provided for in this Indenture
relating to the proposed action have been complied with; and

                  (2) an Opinion of Counsel stating that, in the opinion of such
counsel, all such conditions precedent have been complied with.

         SECTION 13.05.    STATEMENTS REQUIRED IN CERTIFICATE OR OPINION.

         Each Officers' Certificate or Opinion of Counsel with respect to
compliance with a covenant or condition provided for in this Indenture shall
include:

                  (1) a statement that each individual making such Officers'
         Certificate or Opinion of Counsel has read such covenant or condition;

                  (2) a brief statement as to the nature and scope of the
examination or investigation upon which the statements or opinions contained in
such Officers' Certificate or Opinion of Counsel are based;

                  (3) a statement that, in the opinion of each such individual,
he or she has made such examination or investigation as is necessary to enable
him or her to express an informed opinion as to whether or not such covenant or
condition has been complied with; and

                  (4) a statement that, in the opinion of such individual, such
covenant or condition has been complied with.

         SECTION 13.06.    SEPARABILITY CLAUSE.

         In case any provision in this Indenture or in the Securities shall be
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not in any way be affected or impaired thereby.

         SECTION 13.07.    RULES BY TRUSTEE, PAYING AGENT, CONVERSION AGENT AND
REGISTRAR.

         The Trustee may make reasonable rules for action by or a meeting of
Holders. The Registrar, Conversion Agent and the Paying Agent may make
reasonable rules for their functions.

                                       62
<PAGE>   69

         SECTION 13.08.    GOVERNING LAW.

         THE LAWS OF THE STATE OF NEW YORK SHALL GOVERN THIS INDENTURE AND THE
SECURITIES.

         SECTION 13.09.    NO RECOURSE AGAINST OTHERS.

         A director, officer, employee or stockholder, as such, of the Company
shall not have any liability for any obligations of the Company under the
Securities or this Indenture or for any claim based on, in respect of or by
reason of such obligations or their creation. By accepting a Security, each
Holder shall waive and release all such liability. The waiver and release shall
be part of the consideration for the issue of the Securities.

         SECTION 13.10.    RECORD DATE FOR VOTE OR CONSENT OF SECURITYHOLDERS.

         The Company may set a record date for purposes of determining the
identity of Holders entitled to vote or consent to any action by vote or consent
authorized or permitted under this Indenture, which record date shall be the
later of 10 days prior to the first solicitation of such vote or consent or the
date of the most recent list of Holders furnished to the Trustee pursuant to
Section 2.05 prior to such solicitation. If a record date is fixed, those
Persons who were Holders at such record date (or their duly designated proxies),
and only those Persons, shall be entitled to take such action by vote or consent
or to revoke any vote or consent previously given, whether or not such Persons
continue to be Holders after such record date.

         SECTION 13.11.    RULES BY TRUSTEE, PAYING AGENT, REGISTRAR.

         The Trustee may make reasonable rules for action by or at a meeting of
Holders. The Registrar or the Paying Agent may make reasonable rules for its
functions.

         SECTION 13.12.    SUCCESSORS.

         All agreements of the Company in this Indenture and the Securities
shall bind its successor. All agreements of the Trustee in this Indenture shall
bind its successor.

         SECTION 13.13.    MULTIPLE ORIGINALS.

         The parties may sign any number of copies (including by facsimile) of
this Indenture. Each signed copy shall be an original, but all of them together
represent the same agreement. One signed copy is enough to prove this Indenture.

                            (SIGNATURE PAGE FOLLOWS)

                                       63

<PAGE>   70

         IN WITNESS WHEREOF, the undersigned, being duly authorized, have
executed this Indenture on behalf of the respective parties hereto as of the
date first written above.

                              NABORS INDUSTRIES, INC.

                              By:           /s/ Daniel McLachlin
                                   ---------------------------------------
                                  Name:   Daniel McLachlin
                                  Title:  Vice President - Administration
                                                & Secretary

                              BANK ONE, N.A., as Trustee

                              By:           /s/ David B. Knox
                                   ---------------------------------------
                                  Name:   David B. Knox
                                  Title:  Authorized Signer

                                       64
<PAGE>   71

                                    EXHIBIT A

                           [FORM OF FACE OF SECURITY]

FOR UNITED STATES FEDERAL INCOME TAX PURPOSES, THIS SECURITY BEARS ORIGINAL
ISSUE DISCOUNT. INFORMATION INCLUDING THE ISSUE PRICE, AMOUNT OF ORIGINAL ISSUE
DISCOUNT, THE ISSUE DATE, AND THE YIELD TO MATURITY WILL BE MADE AVAILABLE TO
HOLDERS UPON REQUEST TO THE CHIEF FINANCIAL OFFICER OF THE COMPANY, AT (281)
874-0035.

                      [FORM OF LEGEND FOR GLOBAL SECURITY]

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE COMPANY OR ITS
AGENT FOR REGISTRATION OF TRANSFERS, EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

TRANSFERS OF THIS GLOBAL SECURITY SHALL BE LIMITED TO TRANSFER IN WHOLE, BUT NOT
IN PART, TO NOMINEES OF DTC OR TO A SUCCESSOR THEREOF OR SUCH SUCCESSOR'S
NOMINEE AND TRANSFERS MADE IN ACCORDANCE WITH THE RESTRICTIONS SET FORTH IN THE
INDENTURE REFERRED TO ON THE REVERSE HEREOF.

                          [RESTRICTED SECURITY LEGEND]

THE DEBENTURE EVIDENCED HEREBY HAS NOT BEEN REGISTERED UNDER THE UNITED STATES
SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), OR ANY STATE
SECURITIES LAWS, AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD WITHIN THE UNITED
STATES OR TO, OR FOR THE ACCOUNT OR BENEFIT OF, UNITED STATES PERSONS EXCEPT AS
SET FORTH IN THE FOLLOWING SENTENCE. BY ITS ACQUISITION HEREOF, THE HOLDER (1)
REPRESENTS THAT (A) IT IS A "QUALIFIED INSTITUTIONAL BUYER" (AS DEFINED IN RULE
144A UNDER THE SECURITIES ACT) OR (B) NOT A UNITED STATES PERSON AND IS OUTSIDE
THE UNITED STATES WITHIN THE MEANING OF (OR AN ACCOUNT SATISFYING THE
REQUIREMENTS OF PARAGRAPH (K)(2) OF RULE 902 UNDER) REGULATION S UNDER THE
SECURITIES ACT, OR (C) IT IS AN INSTITUTIONAL "ACCREDITED INVESTOR" (AS DEFINED
IN RULE 501(a)(1), (2), (3) OR (7) UNDER THE SECURITIES ACT) ("INSTITUTIONAL
ACCREDITED INVESTOR"); (2) AGREES THAT IT WILL NOT, PRIOR TO EXPIRATION OF THE
HOLDING PERIOD APPLICABLE TO SALES OF THE

                                       1
<PAGE>   72

DEBENTURE EVIDENCED HEREBY UNDER RULE 144(k) UNDER THE SECURITIES ACT (OR ANY
SUCCESSOR PROVISION), RESELL OR OTHERWISE TRANSFER THE DEBENTURE EVIDENCED
HEREBY OR THE COMMON STOCK ISSUABLE UPON CONVERSION OF SUCH DEBENTURE WITHIN THE
UNITED STATES OR TO OR FOR THE ACCOUNT OF U.S. PERSON EXCEPT (A) TO NABORS
INDUSTRIES, INC. OR ANY SUBSIDIARY THEREOF, (B) TO A QUALIFIED INSTITUTIONAL
BUYER IN COMPLIANCE WITH RULE 144A UNDER THE SECURITIES ACT, (C) TO AN
INSTITUTIONAL ACCREDITED INVESTOR THAT PRIOR TO SUCH TRANSFER FURNISHES TO BANK
ONE, N.A., AS TRUSTEE (OR A SUCCESSOR TRUSTEE, AS APPLICABLE), A SIGNED LETTER
CONTAINING CERTAIN REPRESENTATIONS AND AGREEMENTS RELATING TO THE RESTRICTIONS
ON TRANSFER OF THE DEBENTURE EVIDENCED HEREBY (THE FORM OF WHICH LETTER CAN BE
OBTAINED FROM SUCH TRUSTEE OR A SUCCESSOR TRUSTEE, AS APPLICABLE), (D) PURSUANT
TO THE EXEMPTION FROM REGISTRATION PROVIDED BY RULE 144 UNDER THE SECURITIES ACT
(IF AVAILABLE), OR (E) PURSUANT TO A REGISTRATION STATEMENT WHICH HAS BEEN
DECLARED EFFECTIVE UNDER THE SECURITIES ACT (AND WHICH CONTINUES TO BE EFFECTIVE
AT THE TIME OF SUCH TRANSFER), (3) PRIOR TO SUCH TRANSFER (OTHER THAN A TRANSFER
PURSUANT TO CLAUSE 2(E) ABOVE), IT WILL FURNISH TO BANK ONE, N.A., AS TRUSTEE
(OR A SUCCESSOR TRUSTEE, AS APPLICABLE), SUCH CERTIFICATIONS, LEGAL OPINIONS OR
OTHER INFORMATION AS THE TRUSTEE MAY REASONABLY REQUIRE TO CONFIRM THAT SUCH
TRANSFER IS BEING MADE PURSUANT TO AN EXEMPTION FROM OR IN A TRANSACTION NOT
SUBJECT TO THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND (4) AGREES
THAT IT WILL DELIVER TO EACH PERSON TO WHOM THE DEBENTURE EVIDENCED HEREBY IS
TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND IN CONNECTION
WITH ANY TRANSFER OF THE DEBENTURE EVIDENCED HEREBY PRIOR TO THE EXPIRATION OF
THE HOLDING PERIOD APPLICABLE TO SALES OF THE DEBENTURE EVIDENCED HEREBY UNDER
RULE 144(k) UNDER THE SECURITIES ACT (OR ANY SUCCESSOR PROVISION), THE HOLDER
MUST CHECK THE APPROPRIATE BOX SET FORTH ON THE REVERSE HEREOF RELATING TO THE
MANNER OF SUCH TRANSFER AND SUBMIT THIS CERTIFICATE TO BANK ONE, N.A., AS
TRUSTEE (OR A SUCCESSOR TRUSTEE, AS APPLICABLE). IF THE PROPOSED TRANSFEREE IS
AN INSTITUTIONAL ACCREDITED INVESTOR OR IS A PURCHASER WHO IS NOT A UNITED
STATES PERSON, THE HOLDER MUST PRIOR TO SUCH TRANSFER FURNISH TO BANK ONE, N.A.,
AS TRUSTEE (OR A SUCCESSOR TRUSTEE, AS APPLICABLE), SUCH CERTIFICATIONS, LEGAL
OPINIONS OR OTHER INFORMATION AS IT MAY REASONABLY REQUIRE TO CONFIRM THAT SUCH
TRANSFER IS BEING MADE PURSUANT TO AN EXEMPTION FROM, OR IN A TRANSACTION NOT
SUBJECT TO THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT. THIS LEGEND WILL
BE REMOVED UPON THE EARLIER OF THE TRANSFER OF THE DEBENTURE EVIDENCED HEREBY
PURSUANT TO CLAUSE 2(E) ABOVE OR UPON ANY TRANSFER OF THE DEBENTURE EVIDENCED
HEREBY UNDER RULE 144(k) UNDER THE SECURITIES ACT (OR ANY SUCCESSOR PROVISION).
AS USED HEREIN, THE TERMS "UNITED STATES" AND "UNITED STATES PERSON" HAVE THE
MEANINGS GIVEN TO THEM BY REGULATION S UNDER THE SECURITIES ACT.

                                       2
<PAGE>   73

                             NABORS INDUSTRIES, INC.

                ZERO COUPON CONVERTIBLE SENIOR DEBENTURE DUE 2021

No.
Issue Date:  February 5, 2001                  Original Issue Discount:  $391.59
Issue Price:  $608.41                         (for each $1,000 Principal Amount)
(for each $1,000 Principal Amount)

                                                                          CUSIP:

         Nabors Industries, Inc., a Delaware corporation, promises to pay to
______________________ or registered assigns, on February 5, 2021 the Principal
Amount of __________________________________ Dollars ($________________) [or
such greater or lesser Principal Amount as may be shown on Schedule A
hereto].(1)

         This Security shall not bear interest except as specified on the other
side of this Security. Original Issue Discount will accrue as specified on the
other side of this Security. This Security is convertible as specified on the
other side of this Security.

         Additional provisions of this Security are set forth on the other side
of this Security.

         IN WITNESS WHEREOF, Nabors Industries, Inc. has caused this instrument
to be duly executed.

                                     NABORS INDUSTRIES, INC.

                                     By:
                                          --------------------------------------
                                     Name:
                                           -------------------------------------
                                     Title:
                                           -------------------------------------

Dated:
      -------------------

TRUSTEE'S CERTIFICATE OF AUTHENTICATION

___________________, as Trustee, certifies that this is one of the Securities
referred to in the within-mentioned Indenture.

By
   -----------------------------
   Authorized Signatory

----------
(1) For inclusion in the global Security only.

                                       3
<PAGE>   74

                       [FORM OF REVERSE SIDE OF SECURITY]

                             NABORS INDUSTRIES, INC.

                ZERO COUPON CONVERTIBLE SENIOR DEBENTURE DUE 2021

1.   INTEREST

     This Security shall not bear interest except as specified in this paragraph
or in paragraph 10 hereof. If the Principal Amount hereof or any portion of such
Principal Amount is not paid when due (whether upon acceleration pursuant to
Section 6.02 of the Indenture, upon the date set for payment of the Redemption
Price pursuant to paragraph 5 hereof, upon the date set for payment of a
Purchase Price or Fundamental Change Purchase Price pursuant to paragraph 6
hereof or upon the Stated Maturity of this Security), then in each such case the
overdue amount shall bear interest at the rate of 2.5% per annum, compounded
semiannually (to the extent that the payment of such interest shall be legally
enforceable), which interest shall accrue from the date such overdue amount was
due to the date payment of such amount, including interest thereon, has been
made or duly provided for. All such interest shall be payable on demand. The
accrual of such interest on overdue amounts shall be in lieu of, and not in
addition to, the continued accrual of Original Issue Discount.

     The Original Issue Discount (the difference between the Issue Price and the
Principal Amount of the Security) in the period during which a Security remains
outstanding shall accrue at 2.5% per annum, on a semiannual bond equivalent
basis using a 360-day year composed of twelve 30-day months, commencing on the
Issue Date of this Security. Original Issue Discount shall cease to accrue on
the earlier of (a) the date on which the Principal Amount hereof or any portion
of such Principal Amount becomes due and payable and (b) any Redemption Date,
Conversion Date, Fundamental Change Repurchase Date, Repurchase Date or other
date on which such Original Issue Discount (or, if such Securities have been
converted to Semiannual Coupon Debentures following the occurrence of a Tax
Event, interest on such debentures) shall cease to accrue in accordance with
Section 2.08 of the Indenture.

2.   METHOD OF PAYMENT

     Subject to the terms and conditions of the Indenture, the Company will make
payments in respect of the Securities to the Persons who are registered Holders
of Securities at the close of business on the Business Day preceding the
Redemption Date or Stated Maturity, as the case may be, or at the close of
business on a Repurchase Date or Fundamental Change Repurchase Date, as the case
may be. Holders must surrender Securities to the Paying Agent to collect such
payments in respect of the Securities. The Company will pay cash amounts in
money of the United States that at the time of payment is legal tender for
payment of public and private debts. However, the Company may make such cash
payments by check payable in such money.

                                       4
<PAGE>   75

3.   PAYING AGENT, CONVERSION AGENT AND REGISTRAR

     Initially, Bank One, N. A., a national banking association (the "TRUSTEE"),
will act as Paying Agent, Conversion Agent and Registrar. The Company may
appoint and change any Paying Agent, Conversion Agent, Registrar or co-registrar
without notice, other than notice to the Trustee. The Company or any of its
Subsidiaries or any of their Affiliates may act as Paying Agent, Conversion
Agent, Registrar or co-registrar.

4.   INDENTURE

     The Company issued the Securities under an Indenture (the "INDENTURE"),
dated as of February 5, 2001, between the Company and the Trustee. Capitalized
terms used herein and not defined herein have the meanings ascribed thereto in
the Indenture. The Securities are subject to all such terms, and Holders are
referred to the Indenture for a statement of those terms.

     The Securities are general unsecured obligations of the Company limited to
$1,381,200,000 aggregate Principal Amount (subject to Sections 2.02 and 2.07 of
the Indenture). The Indenture does not limit other indebtedness of the Company,
whether secured or unsecured.

5.   REDEMPTION AT THE OPTION OF THE COMPANY

     No sinking fund is provided for the Securities. The Securities are
redeemable as a whole, or from time to time in part, at any time at the option
of the Company at the Redemption Prices set forth below, plus Liquidated
Damages, if any, provided that the Securities are not redeemable prior to
February 5, 2006.

     The table below shows Redemption Prices of a Security per $1,000 Principal
Amount on the dates shown below and at Stated Maturity, which prices reflect
accrued Original Issue Discount calculated to each such date. The Redemption
Price of a Security redeemed between such dates would include an additional
amount reflecting the additional Original Issue Discount accrued since the next
preceding date in the table to the actual Redemption Date.

<TABLE>
<CAPTION>

                                                                               (2)
                                                      (1)               ACCRUED ORIGINAL                (3)
                                                SECURITY ISSUE           ISSUE DISCOUNT           REDEMPTION PRICE
                                                     PRICE                   AT 2.5%                 (1) + (2)
                                               ------------------     ----------------------    ---------------------
<S>                                            <C>                    <C>                       <C>

February 5, 2006......................         $      608.41          $         80.48           $        688.89
February 5, 2007......................                608.41                    97.81                    706.22
February 5, 2008......................                608.41                   115.58                    723.99
February 5, 2009......................                608.41                   133.79                    742.20
February 5, 2010......................                608.41                   152.46                    760.87
February 5, 2011......................                608.41                   171.60                    780.01
February 5, 2012......................                608.41                   191.22                    799.63
February 5, 2013......................                608.41                   211.34                    819.75
February 5, 2014......................                608.41                   231.96                    840.37
February 5, 2015......................                608.41                   253.10                    861.51
February 5, 2016......................                608.41                   274.77                    883.18
February 5, 2017......................                608.41                   296.99                    905.40

</TABLE>

                                       5
<PAGE>   76

<TABLE>
<CAPTION>

                                                                               (2)
                                                      (1)               ACCRUED ORIGINAL                (3)
                                                SECURITY ISSUE           ISSUE DISCOUNT           REDEMPTION PRICE
                                                     PRICE                   AT 2.5%                 (1) + (2)
                                               ------------------     ----------------------    ---------------------
<S>                                            <C>                    <C>                       <C>

February 5, 2018......................                608.41                   319.76                    928.17
February 5, 2019......................                608.41                   343.11                    951.52
February 5, 2020......................                608.41                   367.05                    975.46
February 5, 2021......................                608.41                   391.59                  1,000.00

</TABLE>

     If converted to a Semiannual Coupon Debenture following the occurrence of a
Tax Event, this Security will be redeemable at the Restated Principal Amount
plus interest accrued and unpaid from, and including, the date of such
conversion to, but excluding, the Redemption Date.

6.   REPURCHASE BY THE COMPANY AT THE OPTION OF THE HOLDER; REPURCHASE AT THE
     OPTION OF THE HOLDER UPON A FUNDAMENTAL CHANGE

         (a) Subject to the terms and conditions of the Indenture, the Company
shall become obligated to repurchase, at the option of the Holder, the
Securities held by such Holder on the following Repurchase Dates and at the
following Purchase Prices per $1,000 Principal Amount, together with Liquidated
Damages, if any, upon delivery of a Repurchase Notice containing the information
set forth in the Indenture, at any time during the period from the opening of
business on the date that is 20 Business Days prior to such Repurchase Date
until the close of business on such Repurchase Date and upon delivery of the
Securities to the Paying Agent by the Holder as set forth in the Indenture. Such
Purchase Prices may be paid, at the option of the Company, in cash or by the
issuance and delivery of shares of Common Stock of the Company, or in any
combination thereof.

                  REPURCHASE DATE                     PURCHASE PRICE
                  ----------------                    ---------------
                  February 5, 2006                    $       688.89
                  February 5, 2011                    $       780.01
                  February 5, 2016                    $       883.18

     Securities in denominations larger than $1,000 of Principal Amount may be
repurchased in part, but only in integral multiples of $1,000 of Principal
Amount.

         (b) If prior to a Repurchase Date this Security has been converted to a
Semiannual Coupon Debenture following the occurrence of a Tax Event, the
Purchase Price will be equal to the Restated Principal Amount plus accrued and
unpaid interest from, and including, the date of conversion to, but excluding,
the Repurchase Date.

         (c) At the option of the Holder and subject to the terms and conditions
of the Indenture, the Company shall become obligated to repurchase the
Securities held by such Holder and delivered to the Company or its designated
agent on or before 30 days after the date of the Company's notice of a
Fundamental Change occurring on or prior to February 5, 2021 for a

                                       6
<PAGE>   77

Fundamental Change Purchase Price equal to the Issue Price plus accrued Original
Issue Discount, Liquidated Damages, if any, and interest, if any, to the
Fundamental Change Repurchase Date which Fundamental Change Purchase Price shall
be paid in cash. Securities in denominations larger than $1,000 of Principal
Amount may be repurchased in part in connection with a Fundamental Change, but
only in integral multiples of $1,000 of Principal Amount. If, prior to a
Fundamental Change Repurchase Date, this Security has been converted to a
Semiannual Coupon Debenture following the occurrence of a Tax Event, the
Purchase Price will be equal to the Restated Principal Amount plus accrued and
unpaid interest from, and including, the date of conversion to, but excluding,
the Fundamental Change Repurchase Date.

         (d) Holders have the right to withdraw any Repurchase Notice or
Fundamental Change Repurchase Notice, as the case may be, by delivering to the
Paying Agent a written notice of withdrawal in accordance with the provisions of
the Indenture.

         (e) If cash (and/or securities if permitted under the Indenture)
sufficient to pay a Purchase Price or Fundamental Change Purchase Price, as the
case may be, of all Securities or portions thereof to be repurchased as of the
Repurchase Date or the Fundamental Change Repurchase Date, as the case may be,
is deposited with the Paying Agent on the Business Day following the Repurchase
Date or the Fundamental Change Repurchase Date, as the case may be, Original
Issue Discount (or interest upon conversion to a Semiannual Coupon Debenture
following the occurrence of a Tax Event) ceases to accrue on such Securities (or
portions thereof) on and after such date, and the Holder thereof shall have no
other rights as such (other than the right to receive the Purchase Price or
Fundamental Change Purchase Price, as the case may be, upon surrender of such
Security).

7.   NOTICE OF REDEMPTION AT THE OPTION OF THE COMPANY

     Notice of redemption at the option of the Company will be mailed at least
15 days but not more than 60 days before the Redemption Date to each Holder of
Securities to be redeemed at the Holder's registered address. If money
sufficient to pay the Redemption Price of all Securities (or portions thereof)
to be redeemed on the Redemption Date is deposited with the Paying Agent prior
to or on the Redemption Date, on and after such date original Issue Discount (or
interest upon conversion to a Semiannual Coupon Debenture following the
occurrence of a Tax Event) ceases to accrue on such Securities or portions
thereof. Securities in denominations larger than $1,000 of Principal Amount may
be redeemed in part but only in multiples of $1,000 of Principal Amount.

8.   RANKING

     The Securities rank equally in contractual right of payment with all of the
other existing and future unsubordinated indebtedness of the Company.

9.   CONVERSION

     Subject to the next two succeeding sentences, a Holder of a Security may
convert this Security for Common Stock of the Company at any time prior to
maturity. If this Security is

                                       7
<PAGE>   78

called for redemption, the Holder may convert it at any time before the close of
the last Trading Day prior to the Redemption Date. A Security in respect of
which a Holder has delivered a notice of exercise of the option to require the
Company to repurchase such Security or to repurchase such Security in the event
of a Fundamental Change may be converted only if the notice of exercise is
withdrawn in accordance with the terms of the Indenture.

     The initial Conversion Rate is 7.0745 shares of Common Stock per $1,000
Principal Amount, subject to adjustment in certain events described in the
Indenture. The Company will deliver cash or a check in lieu of any fractional
share of Common Stock.

     The Holders' right to convert Securities into shares of Common Stock is
subject to the Company's right to elect to instead pay such Holder the amount of
cash set forth in the next succeeding sentence in lieu of delivering all or part
of such shares of Common Stock; PROVIDED, HOWEVER, that if such payment of cash
is not permitted pursuant to the provisions of the Indenture or the provisions
of any other agreement or instrument to which the Company is a party or by which
it is bound or otherwise, the Company shall deliver shares of Common Stock (and
cash in lieu of fractional shares of Common Stock) in accordance with Article 11
of the Indenture, whether or not the Company has delivered a notice pursuant to
Section 11.02 to the effect that the Securities will be paid in cash. The amount
of cash to be paid for each $1,000 Principal Amount of a Security shall be equal
to the Sale Price of a share of Common Stock on the Trading Day immediately
prior to the related Conversion Date multiplied by the Conversion Rate in effect
on such Trading Day.

     The Company shall not pay cash in lieu of delivering all or part of such
shares of Common Stock upon the conversion of any Security pursuant to the terms
of Article 11 of the Indenture (other than cash in lieu of fractional shares) if
there has occurred (prior to, on or after, as the case may be, the Conversion
Date or the date on which the Company delivers its notice of whether each
Security shall he converted into shares of Common Stock or cash) and is
continuing an Event of Default (other than a default in such payment on such
Securities); PROVIDED, HOWEVER, that this sentence shall not apply in the event
that an Event of Default occurs after such cash is paid.

     In the event the Company exercises its option pursuant to Section 12.01 of
the Indenture to have interest in lieu of Original Issue Discount accrue on the
Security following a Tax Event, the Holder will be entitled on conversion to
receive the same number of shares of Common Stock such Holder would have
received if the Company had not exercised such option. If the Company exercises
such option, Securities surrendered for conversion during the period from the
close of business on any Regular Record Date next preceding any Interest Payment
Date to the opening of business of such Interest Payment Date (except Securities
to be redeemed on the next Interest Payment Date) must be accompanied by payment
of an amount equal to the interest thereon that the Holder is to receive. Except
where Securities surrendered for conversion must be accompanied by payment as
described above, no interest on converted Securities will be payable by the
Company on any Interest Payment Date subsequent to the date of conversion.

     To convert this Security a Holder must (1) complete and manually sign the
conversion notice on the back of this Security (or complete and manually sign a
facsimile of such notice)

                                       8
<PAGE>   79

and deliver such notice to the Conversion Agent, (2) complete and manually sign
the conversion notice to the Company on the back of this Security (or complete
and manually sign a facsimile of such notice) and deliver such notice to the
Company, (3) surrender this Security to the Conversion Agent, (4) furnish
appropriate endorsements and transfer documents if required by the Conversion
Agent, the Company or the Trustee and (5) pay any transfer or similar tax, if
required.

     A Holder may convert a portion of this Security if the Principal Amount of
such portion is $1,000 or an integral multiple of $1,000. No payment or
adjustment will be made for dividends on the Common Stock except as provided in
the Indenture. On conversion of this Security, that portion of accrued Original
Issue Discount attributable to the period from the Issue Date to the Conversion
Date with respect to the converted portion of this Security shall not be
canceled, extinguished or forfeited, but rather shall be deemed to be paid in
full to the Holder thereof through the delivery of the Common Stock (together
with any cash payment in lieu of fractional shares) in exchange for the portion
of this Security being converted pursuant to the terms hereof.

10.  TAX EVENT

         (a) From and after the date (the "TAX EVENT DATE") of the occurrence of
a Tax Event, at the option of the Company, interest in lieu of future Original
Issue Discount shall accrue at 2.5% per annum on a principal amount per Security
(the "RESTATED PRINCIPAL AMOUNT") equal to the Issue Price plus Original Issue
Discount accrued to the date immediately prior to the later of the Tax Event
Date or the date the Company makes its election and shall be payable
semiannually on February 5 and August 5 of each year (each an "INTEREST PAYMENT
DATE") to Holders of record at the close of business on January 15 or July 15
(each a "REGULAR RECORD DATE") immediately preceding such Interest Payment Date.
Interest will be computed on the basis of a 360-day year comprised of twelve
30-day months and will accrue from the most recent date to which interest has
been paid or, if no interest has been paid, from the Tax Event Date.

         (b) Interest on any Security that is payable, and is punctually paid or
duly provided for, on any Interest Payment Date shall be paid to the Person in
whose name that Security is registered at the close of business on the Regular
Record Date for such interest at the office or agency of the Company maintained
for such purpose. Each installment of interest on any Security shall be paid in
same-day funds by transfer to an account maintained by the payee located inside
the United States. In the case of a permanent global Security, interest payable
on any Interest Payment Date will be paid to the Depositary, Euroclear and/or
Clearstream, as the case may be, with respect to that portion of such permanent
global Security held for its account by Cede & Co. or the London office of a
depositary, as the case may be, for the purpose of permitting such party to
credit the interest received by it in respect of such permanent global Security
to the accounts of the beneficial owners thereof.

         (c) Except as otherwise specified with respect to the Securities, any
interest on any Security that is payable, but is not punctually paid or duly
provided for, on any Interest Payment Date (herein called "DEFAULTED INTEREST")
shall forthwith cease to be payable to

                                       9
<PAGE>   80
the Holder thereof on the relevant Regular Record Date by virtue of having been
such Holder, and such Defaulted Interest may be paid by the Company as provided
for in Section 12.02(b) of the Indenture.

11.  CONVERSION ARRANGEMENT ON CALL FOR REDEMPTION

     Any Securities called for redemption, unless surrendered for conversion
before the close of business on the last Trading Day prior to the Redemption
Date, may be deemed to be purchased from the Holders of such Securities at an
amount not less than the Redemption Price, by one or more investment bankers or
other purchasers who may agree with the Company to purchase such Securities from
the Holders, to convert them for Common Stock and to make payment for such
Securities to the Trustee in trust for such Holders.

12.  DENOMINATIONS; TRANSFER; EXCHANGE

     The Securities are in registered form, without coupons, in denominations of
$1,000 of Principal Amount and integral multiples of $1,000. A Holder may
transfer or convert Securities in accordance with the Indenture. The Registrar
may require a Holder, among other things, to furnish appropriate endorsements
and transfer documents and to pay any taxes and fees required by law or
permitted by the Indenture. The Registrar need not transfer or exchange any
Securities selected for redemption (except, in the case of a Security to be
redeemed in part, the portion of the Security not to be redeemed) or any
Securities in respect of which a Repurchase Notice or Fundamental Change
Repurchase Notice has been given and not withdrawn (except, in the case of a
Security to be purchased in part, the portion of the Security not to be
purchased) or any Securities for a period of 15 days before the mailing of
notice of Securities to be redeemed.

13.  PERSONS DEEMED OWNERS

     The registered holder of this Security may be treated as the owner of this
Security for all purposes.

14.  UNCLAIMED MONEY OR SECURITIES

     The Trustee and the Paying Agent shall return to the Company upon written
request any money or securities held by them for the payment of any amount with
respect to the Securities that remains unclaimed for six months, PROVIDED,
HOWEVER, that the Trustee or such Paying Agent, before being required to make
any such return, shall in the event that the Securities are no longer held in
global form, at the expense of the Company cause to be published once in a
newspaper of general circulation in The City of New York or mail to each such
Holder notice that such money or securities remains unclaimed and that, after a
date specified therein, which shall not be less than 30 days from the date of
such publication or mailing, any unclaimed money or securities then remaining
will be returned to the Company. After return to the Company, Holders entitled
to the money or securities must look to the Company for payment as general
creditors unless an applicable abandoned property law designates another Person.

                                       10
<PAGE>   81

15.  AMENDMENT; WAIVER

     Subject to certain exceptions set forth in the Indenture, (i) the Indenture
or the Securities may be amended with the written consent of the Holders of at
least a majority in aggregate Principal Amount of the Securities at the time
outstanding and (ii) certain Defaults and Events of Defaults may be waived with
the written consent of the Holders of a majority in aggregate Principal Amount
of the Securities at the time outstanding. Subject to certain exceptions set
forth in the Indenture, without the consent of any Holder, the Company and the
Trustee may amend the Indenture or the Securities to cure any ambiguity, defect
or inconsistency, or to provide for the assumption of the Company's obligations
to the Holders of the Securities in case of a merger or consolidation or sale of
all or substantially all of the Company's assets; to provide for uncertificated
Securities in addition to or in place of certificated Securities or to make any
change that does not adversely affect the rights of any Holder or to comply with
any requirement of the SEC in connection with the qualification of the Indenture
under the TIA.

16.  DEFAULTS AND REMEDIES

     Under the Indenture, Events of Default include (i) the Company defaults in
the payment of the Principal Amount, Issue Price, Redemption Price, Purchase
Price or a Fundamental Change Purchase Price on any Security when the same
becomes due and payable at its Stated Maturity, upon redemption, upon
declaration, when due for repurchase by the Company or otherwise, and, in the
case of Redemption Price, Purchase Price or a Fundamental Change Purchase Price,
such default continues for 10 days; (ii) the Company defaults in the payment of
accrued Original Issue Discount or Liquidated Damages, and such default
continues for 30 days, or, after exercise of its option pursuant to Section
12.01 of the Indenture following a Tax Event, the Company defaults in the
payment of interest upon any security when such interest becomes due and
payable, and such default continues for a period of 30 days; (iii) failure of
the Company to perform or comply with the provisions of Section 11.02 of the
Indenture, and such failure continues for a period of 20 days; (iv) the Company
fails to comply with any of its agreements or covenants in this Security or the
Indenture (other than those referred to in clauses (i) through (iii) above) and
such failure continues for 90 days after receipt by the Company of a Notice of
Default; and (v) certain events of bankruptcy or insolvency as set forth in the
Indenture. If an Event of Default occurs and is continuing, the Trustee, or the
Holders of at least 25% in aggregate Principal Amount of the Securities at the
time outstanding, may declare all the Securities to be due and payable
immediately. Certain events of bankruptcy or insolvency are Events of Default
which will result in the Securities being declared due and payable immediately
upon the occurrence of such Events of Default.

         Holders may not enforce the Indenture or the Securities except as
provided in the Indenture. The Trustee may refuse to enforce the Indenture or
the Securities unless it receives reasonable indemnity or security. Subject to
certain limitations, Holders of a majority in aggregate Principal Amount of the
Securities at the time outstanding may direct the Trustee in its exercise of any
trust or power. The Trustee may withhold from Holders notice of any continuing
Default (except a Default in payment of amounts specified in clause (i) and (ii)
above) if it determines that withholding notice is in their interests.

                                       11
<PAGE>   82

17.  TRUSTEE DEALINGS WITH THE COMPANY

     The Trustee under the Indenture, in its individual or any other capacity,
may become the owner or pledgee of Securities and may otherwise deal with and
collect obligations owed to it by the Company or its Affiliates and may
otherwise deal with the Company or its Affiliates with the same rights it would
have if it were not Trustee.

18.  NO RECOURSE AGAINST OTHERS

     A director, officer, employee or stockholder, as such, of the Company shall
not have any liability for any obligations of the Company under the Securities
or the Indenture or for any claim based on, in respect of or by reason of such
obligations or their creation. By accepting a Security, each Holder waives and
releases all such liability. The waiver and release are part of the
consideration for the issue of the Securities.

19.  AUTHENTICATION

     This Security shall not be valid until an authorized signatory of the
Trustee manually signs the Trustee's Certificate of Authentication on the other
side of this Security.

20.  ABBREVIATIONS

     Customary abbreviations may be used in the name of a Holder or an assignee,
such as TEN COM (=tenants in common), TENANT (=tenants by the entireties), JT
TEN (=joint tenants with right of survivorship and not as tenants in common),
CUST (=custodian), and U/G/M/A (=Uniform Gift to Minors Act).

21.  REGISTRATION RIGHTS AGREEMENT

     The Holders of Restricted Securities are entitled to the benefits of the
Registration Rights Agreement dated as of January 31, 2001 between the Company
and the Initial Purchaser.

22.  GOVERNING LAW

     THE LAWS OF THE STATE OF NEW YORK SHALL GOVERN THE INDENTURE AND THIS
SECURITY.

23.  INDENTURE TO CONTROL

     In case of any conflict between the provisions of this Security and the
Indenture, the provisions of the Indenture shall control.

                                       12
<PAGE>   83

     The Company will furnish to any Holder upon written request and without
charge a copy of the Indenture and the Registration Rights Agreement. Requests
may be made to:

                           Nabors Industries, Inc.
                           515 West Greens Road, Suite 1200
                           Houston, Texas  77067
                           Attention:  Legal Department

                                       13
<PAGE>   84

                           [FORM OF CONVERSION NOTICE]

                                CONVERSION NOTICE
                             TO THE CONVERSION AGENT

To:      Nabors Industries, Inc.
         c/o Conversion Agent

         The undersigned registered holder of this Security hereby irrevocably
exercises the option to convert this Security, or portion hereof (which is
$1,000 Principal Amount (as defined in the Indenture to which this Security is
subject) or an integral multiple thereof) below designated, for shares of Common
Stock of Nabors Industries, Inc. in accordance with the terms of the Indenture
referred to in this Security, and directs that the shares issuable and
deliverable upon such conversion, together with any check in payment for
fractional shares and any Securities representing any unconverted Principal
Amount hereof, be issued and delivered to the registered holder hereof unless a
different name has been indicated below. If shares or any portion of this
Security not converted are to be issued in the name of a Person other than the
undersigned, the undersigned will pay all transfer taxes payable with respect
thereto.

Dated:
                                           -------------------------------------

                                           -------------------------------------
                                                        Signature(s)

Fill in for registration of shares
if to be delivered, and Securities
if to be issued other than to and in
the name of the registered holder:

-------------------------------------
(Name)

-------------------------------------
(Street Address)

-------------------------------------
(City, state and zip code)

Please print name and address

                                    Principal Amount to be converted
                                    (if less than all):
                                    $_________,000
                                    Social Security or Other Taxpayer
                                    Identification Number: ____________

                                       14
<PAGE>   85

                           [FORM OF CONVERSION NOTICE]

                                   CONFIRMING
                                CONVERSION NOTICE
                            TO BE SENT TO THE COMPANY

To:      Nabors Industries, Inc.

         The undersigned registered holder of this Security hereby irrevocably
exercises the option to convert this Security, or portion hereof (which is
$1,000 Principal Amount (as defined in the Indenture to which this Security is
subject) or an integral multiple thereof) below designated, for shares of Common
Stock of Nabors Industries, Inc. in accordance with the terms of the Indenture
referred to in this Security, and directs that the shares issuable and
deliverable upon such conversion, together with any check in payment for
fractional shares and any Securities representing any unconverted Principal
Amount hereof, be issued and delivered to the registered holder hereof unless a
different name has been indicated below. If shares or any portion of this
Security not converted are to be issued in the name of a Person other than the
undersigned, the undersigned will pay all transfer taxes payable with respect
thereto.

Dated:
                                           -------------------------------------

                                           -------------------------------------
                                                        Signature(s)

Fill in for registration of shares
if to be delivered, and Securities
if to be issued other than to and in
the name of the registered holder:

-------------------------------------
(Name)

-------------------------------------
(Street Address)

-------------------------------------
(City, state and zip code)

Please print name and address

                                    Principal Amount to be converted
                                    (if less than all):
                                    $_________,000
                                    Social Security or Other Taxpayer
                                    Identification Number: ____________

                                       15
<PAGE>   86

                       [FORM OF OPTION TO ELECT REPURCHASE
                           UPON A FUNDAMENTAL CHANGE]

To:      Nabors Industries, Inc.

         The undersigned registered holder of this Security hereby acknowledges
receipt of a notice from Nabors Industries, Inc. (the "COMPANY") as to the
occurrence of a Fundamental Change with respect to the Company and requests and
instructs the Company to repurchase this Security, or the portion hereof (which
is $1,000 Principal Amount (as defined in the Indenture to which this Security
is subject) or an integral multiple thereof) below designated, in accordance
with the terms of the Indenture referred to in this Security.

Dated:
      ----------------------------------

                                           -------------------------------------
                                                         Signature(s)

                                           Principal Amount to be converted
                                           (if less than all):
                                           $_________,000
                                           Social Security or Other Taxpayer
                                           Identification Number: ____________

                                       16
<PAGE>   87

                                 TRANSFER NOTICE

This Transfer Notice relates to $__________ Principal Amount (as defined in the
Indenture to which the referenced Securities are subject) of the Zero
Convertible Senior Debentures due 2021 of Nabors Industries, Inc., a Delaware
corporation, held by ____________ (the "Transferor").

                (I) or (we) assign and transfer this Security to

--------------------------------------------------------------------------------
              (Print or type assignee's name, address and zip code)

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
               (Insert assignee's social security or tax I.D. no.)

and irrevocably appoint _______________________________ agent to transfer this
Security on the books of the Company. The agent may substitute another to act
for him.

Your Signature:
               -----------------------------------------------------------------
                          (Sign exactly as your name appears on the
                               other side of this Security)
         Date:
              ------------------------------------------------------------------

         Signature Guarantee:(2)
                                ------------------------------------------------

In connection with any transfer of any of the Securities evidenced by this
certificate occurring prior to the date that is two years after the later of the
date of original issuance of such Securities and the last date, if any, on which
such Securities were owned by the Company or any Affiliate of the Company, the
undersigned confirms that such Securities are being transferred:

CHECK ONE BOX BELOW

     (1) [ ]  to Nabors Industries, Inc.; or

     (2) [ ] pursuant to and in compliance with Rule 144A under the Securities
Act of 1933; or

     (3) [ ] pursuant to and in compliance with Regulation S under the
Securities Act of 1933; or

     (4) [ ] pursuant to another available exemption from the registration
requirements of the Securities Act of 1933; or

----------
(2) Signature must be guaranteed by an "eligible guarantor institution" meeting
the requirements of the Registrar which requirements include membership or
participation in the Security Transfer Medallion Program ("STAMP") or such other
"signature guarantee program" as may be determined by the Registrar in addition
to or in substitution for, STAMP, all in accordance with the Securities Exchange
Act of 1934, as amended.

                                       17
<PAGE>   88

     (5)  [ ]  pursuant to an effective registration statement under the
Securities Act of 1933.

          Unless one of the boxes is checked, the Trustee will refuse to
          register any of the Securities evidenced by this certificate in the
          name of any person other than the registered holder thereof; provided,
          however, that if box (3) or (4) is checked, the Trustee may require,
          prior to registering any such transfer of the Securities such legal
          opinions, certifications and other information as it has reasonably
          requested (including, if the transferee is an institutional accredited
          investor as defined in Rule 501(a)(1), (2), (3) or (7) under the
          Securities Act of 1933, a letter signed by such transferee in the form
          of Exhibit B to the Indenture )to confirm that such transfer is being
          made pursuant to an exemption from, or in a transaction not subject
          to, the registration requirements of the Securities Act of 1933.

          Unless the box below is checked, the undersigned confirms that such
          Security is not being transferred to an "affiliate" of the Company as
          defined in Rule 144 under the Securities Act of 1933 (an "Affiliate"):

     (6)  [ ]  The transferee is an Affiliate of the Company.

                                           -------------------------------------
                                           Signature

                                           -------------------------------------
                                           Date

                                           -------------------------------------
                                           Signature Guarantee(3)
----------
(3) Signature must be guaranteed by a commercial bank, trust company or member
firm of the New York Stock Exchange.

                                       18
<PAGE>   89

              TO BE COMPLETED BY PURCHASER IF (2) ABOVE IS CHECKED.

         The undersigned represents and warrants that it is purchasing this Note
for its own account or an account with respect to which it exercises sole
investment discretion and that it and any such account is a "qualified
institutional buyer" within the meaning of Rule 144A under the Securities Act of
1933, and is aware that the sale to it is being made in reliance on Rule 144A
and acknowledges that it has received such information regarding the Company as
the undersigned has requested pursuant to Rule 144A or has determined not to
request such information and that it is aware that the transferor is relying
upon the undersigned's foregoing representations in order to claim the exemption
from registration provided by Rule 144A.

Dated:
       -------------------         ---------------------------------------------
                                   [Signature of executive officer of purchaser]
                                   Name:
                                          --------------------------------------
                                   Title:
                                          --------------------------------------

                                       19
<PAGE>   90

        [FORM OF SCHEDULE FOR ENDORSEMENTS ON GLOBAL SECURITY
TO REFLECT CHANGES IN PRINCIPAL AMOUNT]

                                   SCHEDULE A

                 Changes to Principal Amount of Global Security

<TABLE>
<CAPTION>

                PRINCIPAL AMOUNT OF SECURITIES
                 BY WHICH THIS GLOBAL SECURITY
                 IS TO BE REDUCED OR INCREASED,
                         AND REASON FOR                REMAINING PRINCIPAL AMOUNT       NOTATION
    DATE             REDUCTION OR INCREASE               OF THIS GLOBAL SECURITY         MADE BY
---------------------------------------------------------------------------------------------------
<S>            <C>                                     <C>                              <C>

</TABLE>

                                       20
<PAGE>   91

                                    EXHIBIT B

                            FORM OF CERTIFICATE FROM
                   ACQUIRING INSTITUTIONAL ACCREDITED INVESTOR

Nabors Industries, Inc.
515 West Greens Road, Suite 1200
Houston, Texas  77067

Bank One, N.A.
100 East Broad Street, 8th Floor
Columbus, Ohio  43215

     Re:  Zero Coupon Convertible Senior Debentures due 2021 of Nabors
          Industries, Inc., a Delaware corporation

                              (CUSIP: ___________)

     Reference is hereby made to the Indenture, dated as of February 5, 2001
(the "Indenture"), between Nabors Industries, Inc., as issuer (the "Company"),
and Bank One, N.A., as trustee. Capitalized terms used but not defined herein
shall have the meanings given to them in the Indenture.

     In connection with our proposed purchase of $____________ aggregate
principal amount of:

     (a) [_] a beneficial interest in a Security in global form, or

     (b) [_] a definitive Security,

     we confirm that:

     1. We understand that any subsequent transfer of the Securities or any
beneficial interest therein is subject to certain restrictions and conditions
set forth in the Indenture and the undersigned agrees to be bound by, and not to
resell, pledge or otherwise transfer the Securities or any beneficial interest
therein except in compliance with, such restrictions and conditions and the
United States Securities Act of 1933, as amended (the "Securities Act").

     2. We understand that the offer and sale of the Securities have not been
registered under the Securities Act, and that the Securities and any beneficial
interest therein may not be offered or sold except as permitted in the following
sentence. We agree, on our own behalf and on behalf of any accounts for which we
are acting as hereinafter stated, that if we should sell the Securities or any
beneficial interest therein, we will do so only (A) to the Company or any
subsidiary thereof, (B) in accordance with Rule 144A under the Securities Act to
a "qualified institutional buyer" (as defined therein), (C) to an institutional
"accredited investor" (as defined below) that, prior to such transfer, furnishes
(or has furnished on its behalf by a U.S. broker-

                                       1

<PAGE>   92

dealer) to you a signed letter substantially in the form of this letter and an
Opinion of Counsel in form reasonably acceptable to the Company to the effect
that such transfer is in compliance with the Securities Act, (D) outside the
United States in accordance with Regulation S under the Securities Act, (E)
pursuant to the provisions of Rule 144 under the Securities Act or (F) pursuant
to an effective registration statement under the Securities Act, and we further
agree to provide to any person purchasing the Securities or a beneficial
interest therein from us in a transaction meeting the requirements of clauses
(A) through (E) of this paragraph a notice advising such purchaser that resales
thereof are restricted as stated herein.

     3. We understand that, on any proposed resale of the Securities or a
beneficial interest therein, we and our transferee will be required to furnish
to you such certifications, legal opinions and other information as you may
reasonably require to confirm that the proposed sale complies with the foregoing
restrictions. We further understand that the Securities purchased by us will
bear a legend to the foregoing effect.

     4. We are an institutional "accredited investor" (as defined in Rule
501(a)(1), (2), (3) or (7) of Regulation D under the Securities Act) and have
such knowledge and experience in financial and business matters as to be capable
of evaluating the merits and risks of our investment in the Securities, and we
and any accounts for which we are acting are each able to bear the economic risk
of our or its investment.

     5. We are acquiring the Securities or a beneficial interest therein
purchased by us for our own account or for one or more accounts (each of which
is an institutional "accredited investor") as to each of which we exercise sole
investment discretion.

     You are entitled to rely upon this letter and are irrevocably authorized to
produce this letter or a copy hereof to any interested party in any
administrative or legal proceedings or official inquiry with respect to the
matters covered hereby.

                              [Insert Name of Institutional Accredited Investor]

                               By:
                                  ----------------------------------------------
                                  Name:
                                  Title:

Dated:
       --------------------------

                                       2

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