<PAGE>

                                                                     Exhibit 4.1

                                                                  EXECUTION COPY

                                    SPSS INC.

                  2.50% CONVERTIBLE SUBORDINATED NOTES DUE 2012

                                   ----------

                                    INDENTURE

                           DATED AS OF MARCH 19, 2007

                                   ----------

                        LASALLE BANK NATIONAL ASSOCIATION

                                   AS TRUSTEE

<PAGE>

                                TABLE OF CONTENTS

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Article 1 DEFINITIONS AND INCORPORATION BY REFERENCE.....................      1
   Section 1.01 Definitions..............................................      1
   Section 1.02 Other Definitions........................................      8
   Section 1.03 Trust Indenture Act Provisions...........................      9
   Section 1.04 Rules of Construction....................................      9
Article 2 THE SECURITIES.................................................     11
   Section 2.01 Form and Dating..........................................     11
   Section 2.02 Execution and Authentication.............................     12
   Section 2.03 Registrar, Paying Agent and Conversion Agent.............     13
   Section 2.04 Paying Agent to Hold Money in Trust......................     13
   Section 2.05 Lists of Holders of Securities...........................     14
   Section 2.06 Transfer and Exchange....................................     14
   Section 2.07 Replacement Securities...................................     15
   Section 2.08 Outstanding Securities...................................     15
   Section 2.09 Treasury Securities......................................     16
   Section 2.10 Temporary Securities.....................................     16
   Section 2.11 Cancellation.............................................     16
   Section 2.12 Legend; Additional Transfer and Exchange Requirements....     16
   Section 2.13 CUSIP Numbers............................................     19
Article 3 PURCHASE UPON FUNDAMENTAL CHANGE...............................     21
   Section 3.01 Purchase at Holders' Option upon a Fundamental Change....     21
   Section 3.02 Effect of Fundamental Change Purchase Notice.............     23
   Section 3.03 Deposit of Fundamental Change Purchase Price.............     23
   Section 3.04 Repayment to The Company.................................     24
   Section 3.05 Securities Purchased in Part.............................     24
   Section 3.06 Compliance with Securities Laws upon Purchase of
                Securities...............................................     24
   Section 3.07 Purchase of Securities in Open Market....................     25
Article 4 CONVERSION.....................................................     26
   Section 4.01 Conversion Privilege and Conversion Rate.................     26
   Section 4.02 Conversion Procedure.....................................     29
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                                TABLE OF CONTENTS

<TABLE>
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   Section 4.03 Fractional Shares........................................     30
   Section 4.04 Taxes on Conversion......................................     31
   Section 4.05 Company to Provide Stock.................................     31
   Section 4.06 Adjustment of Conversion Rate............................     31
   Section 4.07 No Adjustment............................................     37
   Section 4.08 Notice of Adjustment.....................................     38
   Section 4.09 Notice of Certain Transactions...........................     38
   Section 4.10 Effect of Recapitalization, Reclassification,
                Consolidation, Merger or Sale............................     38
   Section 4.11 Trustee's Disclaimer.....................................     39
   Section 4.12 Voluntary Increase.......................................     39
   Section 4.13 Payment of Cash in Lieu of Common Stock..................     40
   Section 4.14 Physical Settlement Election.............................     41
Article 5 COVENANTS......................................................     42
   Section 5.01 Payment of Securities....................................     42
   Section 5.02 SEC and Other Reports....................................     42
   Section 5.03 Compliance Certificates..................................     42
   Section 5.04 Further Instruments and Acts.............................     43
   Section 5.05 Maintenance of Corporate Existence.......................     43
   Section 5.06 Rule 144A Information Requirement........................     43
   Section 5.07 Stay, Extension and Usury Laws...........................     43
   Section 5.08 Payment of Additional Interest...........................     43
   Section 5.09 Maintenance of Office or Agency..........................     44
Article 6 CONSOLIDATION; MERGER; CONVEYANCE; TRANSFER OR LEASE...........     45
   Section 6.01 Company May Consolidate, Etc., Only on Certain Terms.....     45
   Section 6.02 Successor Substituted....................................     45
Article 7 DEFAULT AND REMEDIES...........................................     46
   Section 7.01 Events of Default........................................     46
   Section 7.02 Acceleration.............................................     47
   Section 7.03 Other Remedies...........................................     48
   Section 7.04 Waiver of Defaults and Events of Default.................     48
</TABLE>


                                       ii

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                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
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   Section 7.05 Control by Majority......................................     48
   Section 7.06 Limitations on Suits.....................................     49
   Section 7.07 Rights of Holders to Receive Payment and to Convert......     49
   Section 7.08 Collection Suit by Trustee...............................     49
   Section 7.09 Trustee May File Proofs of Claim.........................     49
   Section 7.10 Priorities...............................................     50
   Section 7.11 Undertaking for Costs....................................     50
Article 8 TRUSTEE........................................................     51
   Section 8.01 Obligations of Trustee...................................     51
   Section 8.02 Rights of Trustee........................................     52
   Section 8.03 Individual Rights of Trustee.............................     53
   Section 8.04 Trustee's Disclaimer.....................................     53
   Section 8.05 Notice of Default or Events of Default...................     53
   Section 8.06 Reports by Trustee to Holders............................     53
   Section 8.07 Compensation and Indemnity...............................     54
   Section 8.08 Replacement of Trustee...................................     55
   Section 8.09 Successor Trustee by Merger, Etc.........................     55
   Section 8.10 Eligibility; Disqualification............................     55
   Section 8.11 Preferential Collection of Claims Against Company........     56
Article 9 SATISFACTION AND DISCHARGE OF INDENTURE........................     57
   Section 9.01 Satisfaction and Discharge of Indenture..................     57
   Section 9.02 Application of Trust Money...............................     57
   Section 9.03 Repayment to Company.....................................     57
   Section 9.04 Reinstatement............................................     58
Article 10 AMENDMENTS; SUPPLEMENTS AND WAIVERS...........................     59
   Section 10.01 Without Consent of Holders..............................     59
   Section 10.02 With Consent of Holders.................................     59
   Section 10.03 Compliance with Trust Indenture Act.....................     60
   Section 10.04 Revocation and Effect of Consents.......................     60
   Section 10.05 Notation on or Exchange of Securities...................     61
</TABLE>


                                       iii

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                                TABLE OF CONTENTS

<TABLE>
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   Section 10.06 Trustee to Sign Amendments, Etc.........................     61
   Section 10.07 Effect of Supplemental Indentures.......................     61
Article 11 SUBORDINATION.................................................     62
   Section 11.01 Agreement to Subordinate................................     62
   Section 11.02 Payment to Holders......................................     62
   Section 11.03 Subrogation of Securities...............................     64
   Section 11.04 Authorization to Effect Subordination...................     65
   Section 11.05 Notice to Trustee.......................................     65
   Section 11.06 Trustee's Relation to Senior Indebtedness...............     66
   Section 11.07 No Impairment of Subordination..........................     66
   Section 11.08 Certain Conversions Deemed Payment......................     67
   Section 11.09 Article Applicable to Paying Agents.....................     67
   Section 11.10 Senior Indebtedness Entitled to Rely....................     67
   Section 11.11 Reinstatement...........................................     67
   Section 11.12 Actions by Holders of Senior Indebtedness...............     68
Article 12 MISCELLANEOUS.................................................     69
   Section 12.01 Trust Indenture Act Controls............................     69
   Section 12.02 Notices.................................................     69
   Section 12.03 Communications By Holders with Other Holder.............     70
   Section 12.04 Certificate and Opinion as to Conditions Precedent......     70
   Section 12.05 Record Date for Vote or Consent of Holders of
                 Securities..............................................     70
   Section 12.06 Rules by Trustee, Paying Agent, Registrar and
                 Conversion Agent........................................     71
   Section 12.07 Legal Holidays..........................................     71
   Section 12.08 Governing Law...........................................     71
   Section 12.09 No Adverse Interpretation of Other Agreements...........     71
   Section 12.10 No Recourse Against Others..............................     71
   Section 12.11 No Security Interest Created............................     71
   Section 12.12 Successors..............................................     71
   Section 12.13 Multiple Counterparts...................................     71
   Section 12.14 Separability............................................     72
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                                TABLE OF CONTENTS

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   Section 12.15 Table of Contents, Headings, Etc........................     72

Exhibit A................................................................    A-1
</TABLE>


                                        v

<PAGE>

                             CROSS REFERENCE TABLE*

<TABLE>
<CAPTION>
TIA                                                                INDENTURE
SECTION                                                             SECTION
-------                                                        -----------------
<S>       <C>                                                  <C>
Section   310...............................................   12.01
          310(a)(1).........................................   8.10
          (a)(2)............................................   8.10
          (a) (3)...........................................   N.A.**
          (a) (4)...........................................   N.A.
          (a) (5)...........................................   8.10
          (b)...............................................   8.10
          (c)...............................................   N.A.
Section   311...............................................   12.01
          311 (a)...........................................   8.11
          (b)...............................................   8.11
          (c)...............................................   N.A.
Section   312...............................................   12.01
          312(a)............................................   2.05
          (b)...............................................   12.03
          (c)...............................................   12.03
Section   313...............................................   12.01
          313(a)............................................   8.06(a)
          (b)(1)............................................   N.A.
          (b)(2)............................................   8.06(a)
          (c)...............................................   8.06(a)
          (d)...............................................   8.06(b)
Section   314...............................................   12.01
          314(a)............................................   5.02(a); 5.03
          (b)...............................................   N.A.
          (c)(1)............................................   2.02; 9.01; 12.04
          (c)(2)............................................   9.01; 12.04
          (c)(3)............................................   N.A.
          (d)...............................................   N.A.
          (e)...............................................   12.04
          (f)...............................................   N.A.
Section   315...............................................   12.01
          315(a)............................................   8.01(b)
          (b)...............................................   8.05
          (d)...............................................   8.01(c)
          (d)(2)............................................   8.01(c)
          (d)(3)............................................   8.01(c)
          (e)...............................................   7.11
Section   316...............................................   12.01
          316 (a)...........................................   7.05; 10.02 (b)
          (b)...............................................   7.07
          (c)...............................................   12.05
Section   317...............................................   7.08; 7.09; 12.01
Section   318...............................................   12.01
</TABLE>

----------
*    This Cross-Reference Table shall not, for any purpose, be deemed a part of
     this Indenture.

**   N.A. means Not Applicable.
<PAGE>

     THIS INDENTURE dated as of March 19, 2007 is between SPSS Inc., a
corporation duly organized under the laws of the State of Delaware (the
"Company"), and LaSalle Bank National Association, a national banking
association organized and existing under the laws of the United States, as
Trustee (the "Trustee").

     In consideration of the purchase of the Securities (as defined herein) by
the Holders thereof, both parties agree as follows for the benefit of the other
and for the equal and ratable benefit of the Holders of the Securities.

                                    ARTICLE 1

                   DEFINITIONS AND INCORPORATION BY REFERENCE

     Section 1.01 Definitions.

     "Additional Interest" has the meaning specified in the Registration Rights
Agreement. All references herein to interest accrued or payable as of any date
shall include any Additional Interest accrued or payable as of such date as
provided in the Registration Rights Agreement.

     "Affiliate" means, with respect to any specified person, 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 person means the power to direct 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.

     "Agent" means any Registrar, Bid Solicitation Agent, Paying Agent or
Conversion Agent.

     "Aggregate Share Cap" means initially 26.3 shares of Common Stock per
$1,000 principal amount of Securities, subject to proportional adjustment in the
same manner as the Conversion Rate upon the occurrence of any of the events
described in clauses (1) through (4) under Section 4.06(a).

     "Applicable Procedures" means, with respect to any transfer or exchange of
beneficial ownership interests in a Global Security, the rules and procedures of
the Depositary, to the extent applicable to such transfer or exchange.

     "Beneficial Ownership" means the definition such term is given in
accordance with Rule 13d-3 promulgated by the SEC under the Exchange Act.

     "Bid Solicitation Agent" means an independent nationally recognized
investment banking firm selected by the Company to determine the Trading Price
for the Securities pursuant to Article 4.

     "Board of Directors" means either the board of directors of the Company or
any committee of the Board of Directors authorized to act for it with respect to
this Indenture.

     "Business Day" means any weekday that is not a day on which banking
institutions in The City of New York or The City of Chicago are authorized or
obligated to close.

     "Capital Stock" of any Person means any and all shares, interests, rights
to purchase, warrants, options, participations or other equivalents of or
interests in (however designated) equity of such Person, but excluding any debt
securities convertible into such equity.


                                        1

<PAGE>

     "Cash" or "cash" means such coin or currency of the United States as at any
time of payment is legal tender for the payment of public and private debts.

     "Certificated Security" means a Security that is in substantially the form
attached as Exhibit A but that does not include the information or the schedule
called for by footnote 1 thereof.

     "Change of Control" means the occurrence of any of the following after the
date hereof: (i) any Person, other than the Company, any of its subsidiaries or
any employee benefit plan of the Company, files a Schedule 13D or a Schedule TO
(or any successor schedule, form or report) pursuant to the Exchange Act
disclosing that such person has become the beneficial owner, directly or
indirectly, through a purchase, merger or other acquisition transaction or
series of transactions, of shares of the Company's Capital Stock entitling that
Person to exercise 50% or more of the total voting power of all shares of the
Company's Capital Stock entitled to vote generally in elections of directors; or
(ii) the consolidation or merger of the Company with or into any other Person,
any merger of another Person into the Company, or any conveyance, transfer,
sale, lease or other disposition of all or substantially all of the Company's
properties and assets to another Person other than to one or more of the
Company's wholly-owned subsidiaries, provided that this clause (ii) shall not
apply to (A) any transaction (x) that does not result in any reclassification,
conversion, exchange or cancellation of outstanding shares of the Company's
Capital Stock and (y) pursuant to which holders of the Company's Capital Stock
immediately prior to the transaction have the entitlement to exercise, directly
or indirectly, 50% or more of the total voting power of all shares of the
Capital Stock entitled to vote generally in elections of directors of the
continuing or surviving Person immediately after the transaction; or (B) any
merger solely for the purpose of changing the Company's jurisdiction of
incorporation and resulting in a reclassification, conversion or exchange of
outstanding shares of Common Stock solely into shares of common stock of the
surviving entity. Notwithstanding anything to the contrary set forth herein, it
will not constitute a Change of Control if 90% or more of the consideration for
the Common Stock (excluding cash payments for fractional shares and cash
payments made in respect of dissenters' appraisal rights) in the transaction or
transactions consists of common stock or American Depositary Shares representing
shares of common stock, in each case which are traded on a U.S. national
securities exchange, or which will be so traded when issued or exchanged in
connection with the transaction or transactions.

     "Closing Price" means on any Trading Day, the reported last sale price per
share (or if no last sale price is reported, the average of the bid and ask
prices per share or, if more than one in either case, the average of the average
bid and the average ask prices per share) on such date reported by the Nasdaq
Global Market or, if the Common Stock (or the applicable security) is not quoted
or listed for trading on the Nasdaq Global Market, as reported by the principal
national or regional securities exchange on which the Common Stock (or such
other security) is listed. If the Common Stock (or such other security) is not
listed for trading on a United States national or regional securities exchange
and not reported by the Nasdaq Global Market on the relevant date, the "Closing
Price" shall be the last quoted bid price for the Common Stock (or such other
security) in the over-the-counter market on the relevant date as reported by the
National Quotation Bureau or similar organization. If the Common Stock (or such
other security) is not so quoted, the "Closing Price" shall be the average of
the midpoint of the last bid and ask prices for the Common Stock (or such other
security) on the relevant date from each of at least three independent
nationally recognized investment banking firms selected by the Company for this
purpose.

     "Common Stock" means the common stock of the Company, par value $0.01 per
share as it exists on the date of this Indenture and any shares of any class or
classes of Capital Stock of the Company resulting from any reclassification or
reclassifications thereof, or, in the event of a merger, consolidation or other
similar transaction involving the Company that is otherwise permitted hereunder
in which the Company is not the surviving corporation the common stock, common
equity interests, ordinary shares or depositary shares or other certificates
representing common equity interests of such surviving corporation


                                        2

<PAGE>

or its direct or indirect parent corporation, 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, however, that if at any time
there shall be more than one such resulting class, the shares of each such class
then so issuable on conversion of Securities shall be substantially in the
proportion which the total number of shares of such class 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 such in the first paragraph of this
Indenture until a successor replaces it pursuant to the applicable provisions of
this Indenture, and thereafter "Company" shall mean such successor Company.

     "Conversion Price" per share of Common Stock as of any day means the result
obtained by dividing (i) $1,000 by (ii) the then applicable Conversion Rate,
rounded to the nearest cent.

     "Conversion Rate" means the rate at which shares of Common Stock shall be
delivered upon conversion, which rate shall be initially 21.3105 shares of
Common Stock for each $1,000 principal amount of Securities, as adjusted from
time to time pursuant to the provisions of this Indenture.

     "Conversion Reference Period" means:

          (i) for Securities that are converted during the period beginning the
     30th day prior to the Final Maturity Date of the Securities, the fifteen
     consecutive Trading Days beginning on the third Trading Day following the
     Final Maturity Date; and

          (ii) in all other instances, the fifteen consecutive Trading Days
     beginning on the third Trading Day following the Conversion Date.

     "Conversion Value" means, for each $1,000 principal amount of Securities,
the average of the Daily Conversion Values for each of the fifteen consecutive
Trading Days of the Conversion Reference Period.

     "Corporate Trust Office" means the office of the Trustee at which at any
particular time the trust created by this Indenture shall be administered, which
initially will be the office of LaSalle Bank National Association located at 135
S. LaSalle Street, Suite 1560, Chicago, Illinois 60603, Attention Gregory S.
Clarke (SPSS Inc. 2.50% Convertible Subordinated Notes due 2012).

     "Daily Conversion Value" means, with respect to any Trading Day, the
product of (1) the applicable Conversion Rate and (2) the Volume Weighted
Average Price of the Company's Common Stock on such Trading Day.

     "Daily Share Amount" means, for each Trading Day of the Conversion
Reference Period and for each $1,000 principal amount of Securities surrendered
for conversion, a number of shares (but in no event less than zero) equal to (i)
the amount of (a) the Volume Weighted Average Price for such Trading Day
multiplied by the Conversion Rate in effect on the Conversion Date, less (b)
$1,000; divided by (ii) the Volume Weighted Average Price for such Trading Day
multiplied by 15.

     "Default" means, when used with respect to the Securities, any event that
is or, after notice or passage of time, or both, would be, an Event of Default.


                                        3

<PAGE>

     "Designated Senior Indebtedness" means any Senior Indebtedness that is
specifically identified by the Company in the instrument governing or evidencing
the indebtedness or the assumption or guarantee thereof (or related agreements
or documents to which the Company is a party) as "Designated Senior
Indebtedness" for purposes of this Indenture, provided that such instrument,
agreement or other document may place limitations and conditions on the right of
such Senior Indebtedness to exercise the rights of Designated Senior
Indebtedness.

     "Exchange Act" means the Securities Exchange Act of 1934, as amended, and
the rules and regulations promulgated thereunder, as in effect from time to
time.

     "Final Maturity Date" means March 15, 2012.

     "Fundamental Change" means the occurrence of a Change of Control or a
Termination of Trading following the original issuance of the Securities.

     "Fundamental Change Effective Date" means the date on which any Fundamental
Change becomes effective.

     "Fundamental Change Purchase Price" of any Security, means 100% of the
principal amount of the Security to be purchased plus accrued and unpaid
interest, if any, and Additional Interest, if any, to, but excluding, the
Fundamental Change Purchase Date.

     "GAAP" means generally accepted accounting principles in the United States
of America as in effect from time to time, including those set forth in (1) the
opinions and pronouncements of the Accounting Principles Board of the American
Institute of Certified Public Accountants, (2) the statements and pronouncements
of the Public Company Accounting Oversight Board and the Financial Accounting
Standards Board, (3) such other statements by such other entity as approved by a
significant segment of the accounting profession and (4) the rules and
regulations of the SEC governing the inclusion of financial statements
(including pro forma financial statements) in registration statements filed
under the Securities Act and periodic reports required to be filed pursuant to
Section 13 of the Exchange Act, including opinions and pronouncements in staff
accounting bulletins and similar written statements from the accounting staff of
the SEC.

     "Global Security" means a Security in global form that is in substantially
the form attached as Exhibit A and that includes the information and schedule
called for in footnote 1 thereof and which is deposited with the Depositary or
its custodian and registered in the name of the Depositary or its nominee.

     "Holder" or "Holder of a Security" means the person in whose name a
Security is registered on the Registrar's books.

     "Indebtedness" means, with respect to any Person on any date of
determination, without duplication, the principal or face amount of:

          (1) all of such Person's indebtedness, obligations and other
     liabilities, contingent or otherwise, (A) for borrowed money, including
     overdrafts, foreign exchange contracts, currency exchange agreements,
     interest rate protection agreements, and any loans or advances from banks,
     whether or not evidenced by notes or similar instruments, or (B) evidenced
     by credit or loan agreements, bonds, debentures, notes or similar
     instruments, or incurred in connection with the acquisition of any
     property, services or assets, whether or not the recourse of the lender is
     to the whole of such Person's assets or to only a portion thereof, other
     than any account payable or other accrued current liability


                                        4

<PAGE>

     or obligation to trade creditors representing the purchase price or cost of
     materials or services obtained in the ordinary course of business;

          (2) all of such Person's reimbursement obligations and other
     liabilities, contingent or otherwise, with respect to letters of credit,
     bank guarantees, bankers' acceptances, surety bonds, performance bonds or
     other guaranty of contractual performance;

          (3) all of such Person's obligations and other liabilities, contingent
     or otherwise, in respect of leases required, in conformity with GAAP, to be
     accounted for as capitalized lease obligations on such Person's balance
     sheet or for a financing purpose;

          (4) all of such Person's obligations and other liabilities, contingent
     or otherwise, under any lease or related document, including a purchase
     agreement, conditional sale or other title retention agreement, in
     connection with the lease of real property or improvements thereon (or any
     personal property included as part of any such lease) which provides that
     such Person is contractually obligated to purchase or cause a third party
     to purchase the leased property or pay an agreed upon residual value of the
     leased property, including such Person's payment obligations under such
     lease or related document to purchase or cause a third party to purchase
     such leased property or pay an agreed upon residual value of the leased
     property to the lessor;

          (5) all of such Person's obligations, contingent or otherwise, with
     respect to an interest rate or other swap, cap, floor or collar agreement
     or hedge agreement, forward contract or other similar instrument or
     agreement or foreign currency hedge, exchange, purchase or similar
     instrument or agreement;

          (6) all of such Person's direct or indirect guarantees or similar
     agreements by such Person in respect of, and all of such Person's payment
     obligations or monetary liabilities, contingent or otherwise, to purchase
     or otherwise acquire or otherwise assure a creditor against loss in respect
     of, indebtedness, obligations or liabilities of another Person of the kinds
     described in clauses (1) through (5);

          (7) all indebtedness or other obligations of the kind described in
     clauses (1) through (5) to the extent secured by any mortgage, pledge, lien
     or other encumbrance existing on property that is owned or held by such
     Person, regardless of whether the indebtedness or other obligation secured
     thereby shall have been assumed by such Person; and

          (8) any and all deferrals, renewals, extensions, refinancings and
     refundings of, or amendments, modifications or supplements to, any
     indebtedness, obligation or liability of the kinds described in clauses (1)
     through (7).

     "Indenture" means this Indenture as amended or supplemented from time to
time pursuant to the terms of this Indenture, including the provisions of the
TIA that are automatically deemed to be a part of this Indenture by operation of
the TIA.

     "Initial Purchaser" means Merrill Lynch, Pierce, Fenner & Smith
Incorporated.

     "Interest Payment Date" means March 15 and September 15 of each year,
commencing September 15, 2007.

     "Issue Date" of any Security means the date on which the Security was
originally issued or deemed issued as set forth on the face of the Security.


                                        5

<PAGE>

     "Officer" means the Chairman or any Co-Chairman of the Board, any Vice
Chairman of the Board, the Chief Executive Officer, the President, any vice
president, whether or not designated by a number or a word or words added before
or after the title "vice president", the Chief Financial Officer, the Treasurer,
the Controller, the Secretary, any Assistant Controller or any Assistant
Secretary of the Company.

     "Officers' Certificate" means a certificate signed on behalf of the Company
by two Officers; provided, however, that for purposes of Sections 4.08 and 5.03,
"Officers' Certificate" means a certificate signed by (a) the principal
executive officer, principal financial officer or principal accounting officer
of the Company and (b) one other Officer.

     "Opinion of Counsel" means a written opinion from legal counsel reasonably
acceptable to the Trustee. The counsel may be an employee of or counsel to the
Company or the Trustee.

     "Person" or "person" means any individual, corporation, partnership,
limited liability company, joint venture, association, joint-stock company,
trust, unincorporated organization, government or any agency or political
subdivision thereof or any syndicate or group that would be deemed to be a
"person" under Section 13(d)(3) of the Exchange Act or any other entity.

     "Principal" or "principal" of a debt security, including the Securities,
means the principal of the debt security plus, when appropriate, the premium, if
any, on the debt security.

     "Registration Rights Agreement" means the Registration Rights Agreement,
dated as of March 19, 2007, between the Company and the Initial Purchaser, as
amended from time to time in accordance with its terms.

     "Regular Record Date" means, with respect to each Interest Payment Date,
the March 1 or September 1, as the case may be, next preceding such Interest
Payment Date.

     "Representative" means the trustee, agent or representative (if any) for an
issue of Senior Indebtedness.

     "Responsible Officer" means, when used with respect to the Trustee, any
officer within the corporate trust services department of the Trustee with
direct responsibility for the administration of this Indenture and also means,
with respect to a particular corporate trust matter, any other officer to whom
such matter is referred because of such person's knowledge of and familiarity
with the particular subject.

     "Restricted Global Security" means a Global Security that is a Restricted
Security.

     "Restricted Security" means a Security required to bear the restricted
legend set forth in the form of Security annexed as Exhibit A.

     "Rule 144" means Rule 144 under the Securities Act or any successor to such
Rule.

     "Rule 144A" means Rule 144A under the Securities Act or any successor to
such Rule.

     "SEC" means the United States Securities and Exchange Commission.

     "Securities" means up to $150,000,000 million aggregate principal amount of
2.50% Convertible Subordinated Notes due 2012, or any of them (each a
"Security"), as amended or supplemented from time to time, that are issued under
this Indenture.


                                        6

<PAGE>

     "Securities Act" means the Securities Act of 1933, as amended, and the
rules and regulations promulgated thereunder, as in effect from time to time.

     "Securities Custodian" means the Trustee, as custodian with respect to the
Securities in global form, or any successor thereto.

     "Senior Indebtedness" means the principal of, premium (if any), interest,
including any interest accruing after the commencement of any bankruptcy or
similar proceeding, whether or not a claim for post-petition interest is allowed
as a claim in the proceeding, and rent payable on or termination payment with
respect to or in connection with, and all fees, costs, expenses and other
amounts accrued or due on or in connection with, the Company's Indebtedness,
whether secured or unsecured, absolute or contingent, due or to become due,
outstanding on the date of this Indenture or thereafter created, incurred,
assumed, guaranteed or in effect guaranteed by the Company, including all
deferrals, renewals, extensions or refundings of, or amendments, modifications
or supplements to, the foregoing. "Senior Indebtedness" does not include: (i)
any Indebtedness that expressly provides that such Indebtedness will not be
senior in right of payment to the Securities or expressly provides that such
Indebtedness is on parity with or junior in right of payment to the Securities;
and (ii) any Indebtedness to any of the Company's Subsidiaries.

     "Significant Subsidiary" means, in respect of any Person, as of any date of
determination, a Subsidiary of such Person that would constitute a "significant
subsidiary" as such term is defined under Rule 1-02(w) of Regulation S-X under
the Securities Act.

     "Stock Price" means the price paid, or deemed to be paid, per share of the
Common Stock in connection with a Fundamental Change as determined pursuant to
Section 4.01(j).

     "Subsidiary" means, in respect of any Person, any corporation, association,
partnership or other business entity of which more than 50% of the total voting
power of shares of Capital Stock entitled (without regard to the occurrence of
any contingency within the control of such Person to satisfy) to vote in the
election of directors, managers, general partners or trustees thereof is at the
time owned or controlled, directly or indirectly, by (i) such Person, (ii) such
Person and one or more Subsidiaries of such Person, or (iii) one or more
Subsidiaries of such Person.

     "Termination of Trading" means the termination (but not the temporary
suspension) of trading of the Common Stock, which will be deemed to have
occurred if the Common Stock or other common stock into which the Securities are
convertible is neither listed for trading on a United States national securities
exchange, or traded in over-the-counter securities markets, and no American
Depository Shares or similar instruments for such common stock are so listed or
approved for listing in the United States.

     "TIA" means the Trust Indenture Act of 1939, as amended, and the rules and
regulations thereunder as in effect on the date of this Indenture, except to the
extent that the Trust Indenture Act or any amendment thereto expressly provides
for application of the Trust Indenture Act as in effect on another date.

     "Trading Day" means any day on which the Nasdaq Global Market or, if the
Common Stock is not quoted or listed for trading on the Nasdaq Global Market,
the principal national or regional securities exchange on which the Common Stock
is listed, is open for trading or, if the Common Stock is not so listed,
admitted for trading or quoted, any Business Day. A Trading Day only includes
those days that have a scheduled closing time of 4:00 p.m. (New York City time)
or the then standard closing time for regular trading on the relevant exchange
or trading system.


                                        7

<PAGE>

     "Trading Price" of the Securities on any date of determination means the
average of the secondary market bid quotations obtained by the Bid Solicitation
Agent for $5 million principal amount of Securities at approximately 3:30 p.m.,
New York City time, on such determination date from three nationally recognized
securities dealers the Company selects; provided that if three such bids cannot
reasonably be obtained by the Bid Solicitation Agent, but two such bids are
obtained, then the average of the two bids shall be used, and if only one such
bid can reasonably be obtained by the Bid Solicitation Agent, that one bid shall
be used. If the Bid Solicitation Agent cannot reasonably obtain at least one bid
for $5 million principal amount of Securities from a nationally recognized
securities dealer, then the Trading Price per $1,000 principal amount of
Securities will be deemed to be less than 98% of the product of the Closing
Price of the Common Stock and the Conversion Rate.

     "Trustee" means the party named as such in the first paragraph of this
Indenture until a successor replaces it in accordance with the provisions of
this Indenture, and thereafter means the successor.

     "Volume Weighted Average Price" per share of Common Stock on any Trading
Day means such price as displayed on Bloomberg (or any successor service) page
SPSS (equity) VAP in respect of the period from 9:30 a.m. to 4:00 p.m., New York
City time, on such Trading Day; or, if such price is not available, the Volume
Weighted Average Price means the market value per share of Common Stock on such
day as determined by a nationally recognized independent investment banking firm
retained for this purpose by the Company.

     "Voting Stock" of a Person means all classes of Capital Stock or other
interests (including partnership interests) of such Person then outstanding and
normally entitled (without regard to the occurrence of any contingency within
the control of such person to satisfy) to vote in the election of directors,
managers or trustees thereof.

     Section 1.02 Other Definitions.

<TABLE>
<CAPTION>
Term                                       Defined in Section
----                                       ------------------
<S>                                        <C>
"Agent Members".........................           2.01
"Bankruptcy Law"........................           7.01
"Business Combination"..................           4.10
"Company Order".........................           2.02
"Conversion Trigger Price"..............           4.01
"Conversion Agent"......................           2.03
"Conversion Date".......................           4.02
"Current Market Price"..................           4.06
"DTC"...................................           2.01
"Depositary"............................           2.01
"Determination Date"....................           4.06
"Distributed Securities"................           4.06
"Distribution Notice"...................           4.01
"Event of Default"......................           7.01
"Expiration Date".......................           4.06
"Expiration Time".......................           4.06
"Fundamental Change Company Notice".....           3.01
"Fundamental Change Purchase Date"......           3.01
"Fundamental Change Purchase Notice"....           3.01
"Junior Securities".....................          11.08
</TABLE>


                                        8

<PAGE>

<TABLE>
<S>                                        <C>
"Legal Holiday".........................          12.07
"Legend"................................           2.12
"Make Whole Premium"....................           4.01
"NASD"..................................           4.06
"Notice of Default".....................           7.01
"Paying Agent"..........................           2.03
"Payment Blockage Notice"...............          11.02
"Physical Settlement Election"..........           4.14
"Primary Registrar".....................           2.03
"Purchase Agreement"....................           2.01
"Purchased Shares"......................           4.06
"record date"...........................           4.06
"QIB"...................................           2.01
"Receiver"..............................           7.01
"Registrar".............................           2.03
"Rights"................................           4.06
"Rights Plan"...........................           4.06
"Spinoff Securities"....................           4.06
"Spinoff Valuation Period"..............           4.06
"tender offer"..........................           4.06
"Triggering Distribution"...............           4.06
"Waiver Election".......................           4.14
</TABLE>

     Section 1.03 Trust Indenture Act Provisions.

     Whenever this Indenture refers to a provision of the TIA, that provision is
incorporated by reference in and made a part of this Indenture. This Indenture
shall also include those provisions of the TIA required to be included herein by
the provisions of the Trust Indenture Reform Act of 1990. The following TIA
terms used in this Indenture have the following meanings:

     "indenture securities" means the Securities;

     "indenture security holder" means a Holder of a Security;

     "indenture to be qualified" means this Indenture;

     "indenture trustee" or "institutional trustee" means the Trustee; and

     "obligor" on the indenture securities means the Company or any other
obligor on the Securities.

     All other terms used in this Indenture that are defined in the TIA, defined
by TIA reference to another statute or defined by any SEC rule and not otherwise
defined herein have the meanings assigned to them therein.

     Section 1.04 Rules of Construction.

     (a)  Unless the context otherwise requires:


                                        9

<PAGE>

          (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 GAAP;

          (3) words in the singular include the plural, and words in the plural
     include the singular;

          (4) provisions apply to successive events and transactions;

          (5) the term "merger" includes a statutory share exchange and the term
     "merged" has a correlative meaning;

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

          (7) references to agreements and other instruments include subsequent
     amendments thereto; and

          (8) all "Article", "Exhibit" and "Section" references are to Articles,
     Exhibits and Sections, respectively, of or to this Indenture unless
     otherwise specified herein, and the terms "herein," "hereof" and other
     words of similar import refer to this Indenture as a whole and not to any
     particular Article, Section or other subdivision.


                                       10

<PAGE>

                                    ARTICLE 2

                                 THE SECURITIES

     Section 2.01 Form and Dating.

     The Securities and the Trustee's certificate of authentication shall be
substantially in the respective forms set forth in Exhibit A, which Exhibit is
incorporated in and made part of this Indenture. The Securities may have
notations, legends or endorsements required by law, stock exchange or automated
quotation system rule or regulation or usage. 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. The Securities are being offered
and sold by the Company pursuant to a Purchase Agreement dated March 13, 2007
(the "Purchase Agreement") between the Company and the Initial Purchaser, in
transactions exempt from, or not subject to, the registration requirements of
the Securities Act.

     (a) Restricted Global Securities.

     All of the Securities are initially being offered and sold to qualified
institutional buyers as defined in Rule 144A (collectively, "QIBS" or
individually, each a "QIB") in reliance on Rule 144A under the Securities Act
and shall be issued initially in the form of one or more Restricted Global
Securities, which shall be deposited on behalf of the purchasers of the
securities represented thereby with the Trustee, at its Corporate Trust Office,
as custodian for the depositary, The Depository Trust Company ("DTC", and such
depositary, or any successor thereto, being hereinafter referred to as the
"Depositary"), and registered in the name of its nominee, Cede & Co. (or any
successor thereto), for the accounts of participants in the Depositary, duly
executed by the Company and authenticated by the Trustee as hereinafter
provided. The aggregate principal amount of the Restricted Global Securities may
from time to time be increased or decreased by adjustments made on the records
of the Securities Custodian as hereinafter provided, subject in each case to
compliance with the Applicable Procedures.

     (b) Global Securities In General.

     Each Global Security shall represent such of the outstanding Securities as
shall be specified therein and each 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 reduced or increased, as appropriate, to reflect
replacements, exchanges, purchases, or conversions of such Securities. Any
adjustment of the aggregate principal amount of a Global Security to reflect the
amount of any increase or decrease in the amount of outstanding Securities
represented thereby shall be made by the Trustee in accordance with instructions
given by the Holder thereof as required by Section 2.12 and shall be made on the
records of the Trustee and the Depositary.

     Members of, or participants in, the Depositary ("Agent Members") shall have
no rights under this Indenture with respect to any Global Security held on their
behalf by the Depositary or under the Global Security, and the Depositary
(including, for this purpose, its nominee) may be treated by the Company, the
Trustee and any agent of the Company or the Trustee as the absolute owner and
Holder of such Global Security for all purposes whatsoever. Notwithstanding the
foregoing, nothing herein shall (1) prevent the Company, the Trustee or any
agent of the Company or the Trustee from giving effect to any written
certification, proxy or other authorization furnished by the Depositary or (2)
impair, as between the Depositary and its Agent Members, the operation of
customary practices governing the exercise of the rights of a Holder of any
Security.


                                       11

<PAGE>

     (c) Book Entry Provisions.

     The Company shall execute and the Trustee shall, in accordance with this
Section 2.01(c), authenticate and deliver initially one or more Global
Securities that (1) shall be registered in the name of the Depositary or its
nominee, (2) shall be delivered by the Trustee to the Depositary or pursuant to
the Depositary's instructions and (3) shall bear legends substantially to the
following effect:

          "UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE
          OF THE DEPOSITORY TRUST COMPANY TO THE COMPANY OR ITS AGENT FOR
          REGISTRATION OF TRANSFER, 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 THE DEPOSITORY
          TRUST COMPANY (AND ANY PAYMENT HEREON IS MADE TO CEDE & CO. OR TO SUCH
          OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE
          DEPOSITORY TRUST COMPANY), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF
          FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE THE
          REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN. THIS
          SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE
          HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY
          OR A NOMINEE THEREOF. THIS SECURITY IS EXCHANGEABLE FOR SECURITIES
          REGISTERED IN THE NAME OF A PERSON OTHER THAN THE DEPOSITARY OR ITS
          NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE
          AND, UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR
          SECURITIES IN DEFINITIVE FORM, THIS SECURITY MAY NOT BE TRANSFERRED
          EXCEPT AS A WHOLE 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."

     Section 2.02 Execution and Authentication.

     (a) The aggregate principal amount of Securities which may be authenticated
and delivered under this Indenture is limited to $150,000,000 aggregate
principal amount, except as provided in Sections 2.06 and 2.07.

     (b) An Officer shall sign the Securities for the Company by manual or
facsimile signature. Typographic and other minor errors or defects in any such
facsimile signature shall not affect the validity or enforceability of any
Security that has been authenticated and delivered by the Trustee.

     (c) If an officer whose signature is on a Security no longer holds that
office at the time the Trustee authenticates the Security, the Security shall be
valid nevertheless.

     (d) A Security shall not be valid until an authorized signatory of the
Trustee by manual or facsimile signature signs the certificate of authentication
on the Security. The signature shall be conclusive evidence that the Security
has been authenticated under this Indenture.

     (e) The Trustee shall authenticate and make available for delivery
Securities for original issue in the aggregate principal amount of up to
$150,000,000 upon receipt of a written order or orders of


                                       12

<PAGE>

the Company signed by an Officer of the Company (a "Company Order"). The Company
Order shall specify the amount of Securities to be authenticated, shall provide
that all such securities will be represented by a Restricted Global Security and
the date on which each original issue of Securities is to be authenticated.

     (f) The Trustee shall act as the initial authenticating agent. Thereafter,
the Trustee may appoint an authenticating agent acceptable to the Company to
authenticate Securities. An authenticating agent may authenticate Securities
whenever the Trustee may do so. Each reference in this Indenture to
authentication by the Trustee includes authentication by such agent. An
authenticating agent shall have the same rights as an Agent to deal with the
Company or an Affiliate of the Company.

     (g) The Securities shall be issuable only in registered form without
coupons and only in denominations of $1,000 principal amount and any integral
multiple thereof.

     Section 2.03 Registrar, Paying Agent and Conversion Agent.

     (a) The Company shall maintain one or more offices or agencies where
Securities may be presented for registration of transfer or for exchange (each,
a "Registrar"), one or more offices or agencies where Securities may be
presented for payment (each, a "Paying Agent"), one or more offices or agencies
where Securities may be presented for conversion (each, a "Conversion Agent")
and one or more offices or agencies where notices and demands to or upon the
Company in respect of the Securities and this Indenture may be served. The
Company will at all times maintain a Paying Agent, Conversion Agent, Registrar
and an office or agency where notices and demands to or upon the Company in
respect of the Securities and this Indenture may be served. One of the
Registrars (the "Primary Registrar") shall keep a register of the Securities and
of their transfer and exchange.

     (b) The Company shall enter into an appropriate agency agreement with any
Agent not a party to this Indenture, provided that the Agent may be an Affiliate
of the Trustee. The agreement shall implement the provisions of this Indenture
that relate to such Agent. The Company shall notify the Trustee of the name and
address of any Agent not a party to this Indenture. If the Company fails to
maintain a Registrar, Paying Agent, Conversion Agent, or agent for service of
notices and demands in any place required by this Indenture, or fails to give
the foregoing notice, the Trustee shall act as such. The Company or any
Affiliate of the Company may act as Paying Agent (except for the purposes of
Section 5.01 and Article 9).

     (c) The Company hereby initially designates the Trustee as Paying Agent,
Registrar, Securities Custodian and Conversion Agent, and designates the
Corporate Trust Office of the Trustee as an office or agency where notices and
demands to or upon the Company in respect of the Securities and this Indenture
shall be served.

     Section 2.04 Paying Agent to Hold Money in Trust.

     Prior to 12:00 p.m. (noon), New York City time, on each due date of the
payment of principal of, or interest on, any Securities, the Company shall
deposit with the Paying Agent a sum sufficient to pay such principal or interest
so becoming due. Subject to Section 9.03, a Paying Agent shall hold in trust for
the benefit of Holders of Securities or the Trustee all money held by the Paying
Agent for the payment of principal of, or interest on, the Securities, and shall
notify the Trustee of any failure by the Company (or any other obligor on the
Securities) to make any such payment. If the Company or an Affiliate of the
Company acts as Paying Agent, it shall, before 12:00 p.m. (noon), New York City
time, on each due date of the principal of, or interest on, any Securities,
segregate the money and hold it as a separate trust fund. The Company at any
time may require a Paying Agent to pay all money held by it to the Trustee, and
the


                                       13

<PAGE>

Trustee may at any time during the continuance of any Default, upon written
request to a Paying Agent, require such Paying Agent to pay forthwith to the
Trustee all sums so held in trust by such Paying Agent. Upon doing so, the
Paying Agent (other than the Company) shall have no further liability for the
money.

     Section 2.05 Lists of Holders of Securities.

     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 of Securities. If the Trustee is not the Primary Registrar, the Company
shall furnish to the Trustee on or before each Interest Payment Date 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 of Securities.

     Section 2.06 Transfer and Exchange.

     (a) Subject to compliance with any applicable additional requirements
contained in Section 2.12, when a Security is presented to a Registrar with a
request to register a transfer thereof or to exchange such Security for an equal
principal amount of Securities of other authorized denominations, the Registrar
shall register the transfer or make the exchange as requested; provided,
however, that every Security presented or surrendered for registration of
transfer or exchange shall be duly endorsed or accompanied by an assignment form
and, if applicable, a transfer certificate each in the form included in Exhibit
A, and completed in a manner satisfactory to the Registrar and duly executed by
the Holder thereof or its attorney duly authorized in writing. To permit
registration of transfers and exchanges, upon surrender of any Security for
registration of transfer or exchange at an office or agency maintained pursuant
to Section 2.03, the Company shall execute and the Trustee shall authenticate
Securities of a like aggregate principal amount at the Registrar's request. Any
exchange or transfer shall be without charge, except that the Company or the
Registrar may require payment of a sum sufficient to cover any tax, assessment
or other governmental charge that may be imposed in relation thereto; provided
that this sentence shall not apply to any exchange pursuant to Section 2.10,
2.12(a), 3.05, 4.02(e) or 10.05.

     (b) Neither the Company, any Registrar nor the Trustee shall be required to
exchange or register a transfer of any Securities or portions thereof in respect
of which a Fundamental Change Purchase Notice has been delivered and not
withdrawn by the Holder thereof (except, in the case of the purchase of a
Security in part, the portion thereof not to be purchased).

     (c) All Securities issued upon any transfer or exchange of 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
transfer or exchange.

     (d) Any Registrar appointed pursuant to Section 2.03 shall provide to the
Trustee such information as the Trustee may reasonably require in connection
with the delivery by such Registrar of Securities upon transfer or exchange of
Securities.

     (e) 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.

     (f) 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 Agent Members or other
beneficial owners of interests in any Global Security) other than to require
delivery of such certificates and other documentation or evidence as are
expressly required by, and to do so if and


                                       14

<PAGE>

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.

     (a) If any mutilated Security is surrendered to the Company, a Registrar or
the Trustee, or the Company, a Registrar and the Trustee receive evidence to
their satisfaction of the destruction, loss or theft of any Security, and there
is delivered to the Company, the applicable Registrar and the Trustee such
security or indemnity as will be required by them to save each of them harmless,
then, in the absence of notice to the Company, such Registrar 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.

     (b) If any such mutilated, destroyed, lost or stolen Security has become or
is about to become due and payable, or is about to be purchased by the Company
pursuant to Article 3, or converted pursuant to Article 4, the Company in its
discretion may, instead of issuing a new Security, pay, purchase or convert such
Security, as the case may be.

     (c) Upon the issuance of any new Securities under this Section 2.07, the
Company may require the payment of a sum sufficient to cover any tax or other
governmental charge that may be imposed in relation thereto as a result of any
Securities, at the request of any Holder, being issued to a Person other than
such Holder and any other reasonable expenses (including the reasonable fees and
expenses of the Trustee or the Registrar) in connection therewith.

     (d) 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.

     (e) The provisions of this Section 2.07 are (to the extent lawful)
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.

     (a) Securities outstanding at any time are all Securities authenticated by
the Trustee, except for those canceled by it, those purchased pursuant to
Article 3, those converted pursuant to Article 4, those delivered to the Trustee
for cancellation or surrendered for transfer or exchange and those described in
this Section 2.08 as not outstanding.

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

     (c) If a Paying Agent (other than the Company or an Affiliate of the
Company) holds in respect of the outstanding Securities on a Fundamental Change
Purchase Date or the Final Maturity Date money sufficient to pay the principal
of (including premium, if any), accrued interest and Additional Interest, if
any, on Securities (or portions thereof) payable on that date, then on and after
such Fundamental Change Purchase Date or Final Maturity Date, as the case may
be, such Securities (or


                                       15

<PAGE>

portions thereof, as the case may be) shall cease to be outstanding and cash
interest and Additional Interest, if any, on them shall cease to accrue.

     (d) Subject to the restrictions contained in Section 2.09, a Security does
not cease to be outstanding because the Company or an Affiliate of the Company
holds the Security.

     Section 2.09 Treasury Securities.

     In determining whether the Holders of the required principal amount of
Securities have concurred in any notice, direction, waiver or consent,
securities owned by the Company or any other obligor on the Securities or by any
Affiliate of the Company or of such other obligor shall be disregarded, except
that, for purposes of determining whether the Trustee shall be protected in
relying on any such notice, direction, waiver or consent, only Securities which
a Responsible Officer of the Trustee with responsibility for this Indenture
actually knows are so owned shall be so disregarded. Securities so owned which
have been pledged in good faith shall not be disregarded if the pledgee
establishes to the satisfaction of the Trustee the pledgee's right so to act
with respect to the Securities and that the pledgee is not the Company or any
other obligor on the Securities or any Affiliate of the Company or of such other
obligor.

     Section 2.10 Temporary Securities.

     Until definitive Securities are ready for delivery, the Company may prepare
and execute, and, upon receipt of a Company Order, the Trustee shall
authenticate and deliver, temporary Securities. Temporary Securities shall be
substantially in the form of definitive securities but may have variations that
the Company with the consent of the Trustee considers appropriate for temporary
Securities. Without unreasonable delay, the Company shall prepare and the
Trustee shall authenticate and deliver definitive Securities in exchange for
temporary Securities.

     Section 2.11 Cancellation.

     The Company at any time may deliver Securities to the Trustee for
cancellation. The Registrar, the Paying Agent and the Conversion Agent shall
forward to the Trustee or its agent any Securities surrendered to them for
transfer, exchange, purchase, payment or conversion. The Trustee and no one else
shall cancel, in accordance with its standard procedures, all Securities
surrendered for transfer, exchange, purchase, payment, conversion or
cancellation and shall dispose of the cancelled Securities in accordance with
its customary procedures or deliver the canceled Securities to the Company. All
Securities which are purchased or otherwise acquired by the Company or any of
its Subsidiaries prior to the Final Maturity Date pursuant to Article 3 shall be
delivered to the Trustee for cancellation, and the Company may not hold or
resell such Securities or issue any new Securities to replace any such
Securities or any Securities that any Holder has converted pursuant to Article
4.

     Section 2.12 Legend; Additional Transfer and Exchange Requirements.

     (a) If Securities are issued upon the transfer, exchange or replacement of
Securities subject to restrictions on transfer and bearing the legends set forth
on the forms of Securities attached as Exhibit A (collectively, the "Legend"),
or if a request is made to remove the Legend on a Security, the Securities so
issued shall bear the Legend, or the Legend shall not be removed, as the case
may be, unless there is delivered to the Company and the Registrar such
satisfactory evidence, which shall include an Opinion of Counsel if requested by
the Company or such Registrar, as may be reasonably required by the Company and
the Registrar, that neither the Legend nor the restrictions on transfer set
forth therein are required to ensure that transfers thereof comply with the
provisions of Rule 144A or Rule 144 under the Securities


                                       16

<PAGE>

Act or that such Securities are not "restricted" within the meaning of Rule 144
under the Securities Act; provided that no such evidence need be supplied in
connection with the sale of such Security pursuant to a registration statement
that is effective at the time of such sale. Upon (1) provision of such
satisfactory evidence if requested, or (2) notification by the Company to the
Trustee and Registrar of the sale of such Security pursuant to a registration
statement that is effective at the time of such sale, the Trustee, at the
written direction of the Company, shall authenticate and deliver a Security that
does not bear the Legend. If the Legend is removed from the face of a Security
and the Security is subsequently held by an Affiliate of the Company, the Legend
shall be reinstated.

     (b) A Global Security may not be transferred, in whole or in part, to any
Person other than the Depositary or a nominee or any successor thereof, and no
such transfer to any such other Person may be registered; provided that the
foregoing shall not prohibit any transfer of a Security that is issued in
exchange for a Global Security but is not itself a Global Security. No transfer
of a Security to any Person shall be effective under this Indenture or the
Securities unless and until such Security has been registered in the name of
such Person. Notwithstanding any other provisions of this Indenture or the
Securities, transfers of a Global Security, in whole or in part, shall be made
only in accordance with this Section 2.12.

     (c) Subject to Section 2.12(b) and in compliance with Section 2.12(d),
every Security shall be subject to the restrictions on transfer provided in the
Legend. Whenever any Restricted Security other than a Restricted Global Security
is presented or surrendered for registration of transfer or in exchange for a
Security registered in a name other than that of the Holder, such Security must
be accompanied by a certificate in substantially the form set forth in Exhibit
A, dated the date of such surrender and signed by the Holder of such Security,
as to compliance with such restrictions on transfer. The Registrar shall not be
required to accept for such registration of transfer or exchange any Security
not so accompanied by a properly completed certificate.

     (d) The restrictions imposed by the Legend upon the transferability of any
Security shall cease and terminate when such Security has been sold pursuant to
an effective registration statement under the Securities Act or transferred in
compliance with Rule 144 under the Securities Act (or any successor provision
thereto) or, if earlier, upon the expiration of the holding period applicable to
sales thereof under Rule 144(k) under the Securities Act (or any successor
provision). Any Security as to which such restrictions on transfer shall have
expired in accordance with their terms or shall have terminated may, upon a
surrender of such Security for exchange to the Registrar in accordance with the
provisions of this Section 2.12 (accompanied, in the event that such
restrictions on transfer have terminated by reason of a transfer in compliance
with Rule 144 or any successor provision, by, if requested by the Company or the
Registrar, an Opinion of Counsel reasonably acceptable to the Company and the
Registrar and addressed to the Company and the Registrar, to the effect that the
transfer of such Security has been made in compliance with Rule 144 or such
successor provision), be exchanged for a new Security, of like tenor and
aggregate principal amount, which shall not bear the restrictive Legend. The
Company shall inform the Trustee of the effective date of any registration
statement registering the offer and sale of the Securities under the Securities
Act. The Trustee shall not be liable for any action taken or omitted to be taken
by it in good faith in accordance with the aforementioned Opinion of Counsel or
registration statement.

     As used in Sections 2.12(c) and (d), the term "transfer" encompasses any
sale, pledge, transfer, hypothecation or other disposition of any Security.

     (e) The provisions below shall apply only to Global Securities:


                                       17
<PAGE>

          (1) Each Global Security authenticated under this Indenture shall be
     registered in the name of the Depositary or a nominee thereof and delivered
     to such Depositary or a nominee thereof or custodian therefor, and each
     such Global Security shall constitute a single Security for purposes of
     this Indenture.

          (2) Notwithstanding any other provisions of this Indenture or the
     Securities, a Global Security shall not be exchanged in whole or in part
     for a Security registered, and no transfer of a Global Security in whole or
     in part shall be registered in the name of any Person other than the
     Depositary or one or more nominees thereof; provided that a Global Security
     may be exchanged for securities registered in the names of any person
     designated by the Depositary in the event that (A) the Depositary has
     notified the Company that it is unwilling or unable to continue as
     Depositary for such Global Security or such Depositary has ceased to be a
     "clearing agency" registered under the Exchange Act, and a successor
     Depositary is not appointed by the Company within 90 days after receiving
     such notice or becoming aware that the Depositary has ceased to be a
     "clearing agency," or (B) an Event of Default has occurred and is
     continuing with respect to the Securities. Any Global Security exchanged
     pursuant to subclause (A) above shall be so exchanged in whole and not in
     part, and any Global Security exchanged pursuant to subclause (B) above may
     be exchanged in whole or from time to time in part as directed by the
     Depositary. Any Security issued in exchange for a Global Security or any
     portion thereof shall be a Global Security; provided that any such Security
     so issued that is registered in the name of a Person other than the
     Depositary or a nominee thereof shall not be a Global Security.

          (3) Securities issued in exchange for a Global Security or any portion
     thereof shall be issued in definitive, fully registered form, without
     interest coupons, shall have an aggregate principal amount equal to that of
     such Global Security or portion thereof to be so exchanged, shall be
     registered in such names and be in such authorized denominations as the
     Depositary shall designate and shall bear the applicable legends provided
     for herein. Any Global Security to be exchanged in whole shall be
     surrendered by the Depositary to the Trustee, as Registrar. With regard to
     any Global Security to be exchanged in part, either such Global Security
     shall be so surrendered for exchange or, if the Trustee is acting as
     custodian for the Depositary or its nominee with respect to such Global
     Security, the principal amount thereof shall be reduced, by an amount equal
     to the portion thereof to be so exchanged, by means of an appropriate
     adjustment made on the records of the Trustee. Upon any such surrender or
     adjustment, the Trustee shall authenticate and deliver the Security
     issuable on such exchange to or upon the order of the Depositary or an
     authorized representative thereof.

          (4) Subject to clause (6) of this Section 2.12(e), the registered
     Holder may grant proxies and otherwise authorize any Person, including
     Agent Members and Persons that may hold interests through Agent Members, to
     take any action which a Holder is entitled to take under this Indenture or
     the Securities.

          (5) In the event of the occurrence of any of the events specified in
     clause (2) of this Section 2.12(e), the Company will promptly make
     available to the Trustee a reasonable supply of Certificated Securities in
     definitive, fully registered form, without interest coupons.

          (6) At such time as all interests in a Global Security have been
     converted, canceled or exchanged for Securities in certificated form, such
     Global Security shall, upon receipt thereof, be cancelled by the Trustee in
     accordance with standing procedures and instructions existing between the
     Depositary and the Securities Custodian, subject to Section 2.11 of this
     Indenture. At any time prior to such cancellation, if any interest in a
     Global Security is converted, canceled or exchanged for Securities in
     certificated form, the principal amount of such Global Security


                                       18

<PAGE>

     shall, in accordance with the standing procedures and instructions existing
     between the Depositary and the Securities Custodian, be appropriately
     reduced, and an endorsement shall be made on such Global Security, by the
     Trustee or the Securities Custodian, at the direction of the Trustee, to
     reflect such reduction.

     (f) Until the expiration of the holding period applicable to sales thereof
under Rule 144(k) under the Securities Act (or any successor provision thereto),
any stock certificate representing Common Stock issued upon conversion 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 transferred in compliance with Rule 144 under
the Securities Act (or any successor provision thereto), or such Common Stock
has been issued upon conversion of Securities that have been transferred
pursuant to a registration statement that has been declared effective under the
Securities Act or pursuant to Rule 144 under the Securities Act (or any
successor provision thereto), or unless otherwise agreed by the Company in
writing with written notice thereof to the transfer agent:

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 REOFFERED, SOLD, ASSIGNED,
TRANSFERRED, PLEDGED, ENCUMBERED OR OTHERWISE DISPOSED OF IN THE ABSENCE OF SUCH
REGISTRATION OR UNLESS SUCH TRANSACTION IS EXEMPT FROM, OR NOT SUBJECT TO,
REGISTRATION UNDER THE SECURITIES ACT.

BY ITS ACQUISITION HEREOF, THE HOLDER AGREES TO OFFER, SELL OR OTHERWISE
TRANSFER THE COMMON STOCK EVIDENCED HEREBY PRIOR TO THE DATE THAT IS TWO YEARS
AFTER THE LATER OF THE ORIGINAL ISSUE DATE HEREOF AND THE LAST DATE ON WHICH
SPSS INC. (THE "COMPANY") OR ANY AFFILIATE OF THE COMPANY WAS THE OWNER OF THE
COMMON STOCK EVIDENCED HEREBY (OR ANY PREDECESSOR OF THE COMMON STOCK EVIDENCED
HEREBY) (THE "RESALE RESTRICTION TERMINATION DATE") ONLY (A) TO THE COMPANY OR
ANY SUBSIDIARY THEREOF, (B) PURSUANT TO A REGISTRATION STATEMENT WHICH HAS BEEN
DECLARED EFFECTIVE UNDER THE SECURITIES ACT, OR (C) PURSUANT TO ANY OTHER
AVAILABLE EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT,
SUBJECT TO THE COMPANY'S AND THE TRANSFER AGENT'S RIGHT PRIOR TO ANY SUCH OFFER,
SALE OR TRANSFER PURSUANT TO CLAUSE (C) PRIOR TO THE RESALE RESTRICTION
TERMINATION DATE TO REQUIRE THE DELIVERY OF AN OPINION OF COUNSEL,
CERTIFICATIONS AND/OR OTHER INFORMATION SATISFACTORY TO EACH OF THEM, AND IN
EACH OF THE FOREGOING CASES, TO REQUIRE THAT A CERTIFICATE OF TRANSFER IN THE
FORM APPEARING ON THE OTHER SIDE OF THE GLOBAL SECURITY IS COMPLETED AND
DELIVERED BY THE TRANSFEROR TO THE TRANSFER AGENT. THIS LEGEND WILL BE REMOVED
UPON THE REQUEST OF THE HOLDER AFTER THE RESALE RESTRICTION TERMINATION DATE.

     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.

     Section 2.13 CUSIP Numbers.


                                       19

<PAGE>

     The Company in issuing the Securities may use one or more "CUSIP" numbers
(if then generally in use), and, if so, the Trustee shall use "CUSIP" numbers in
notices to Holders 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 such notice and that
reliance may be placed only on the other identification numbers printed on the
Securities, and any such notice 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.


                                       20

<PAGE>

                                    ARTICLE 3

                        PURCHASE UPON FUNDAMENTAL CHANGE

     Section 3.01 Purchase at Holders' Option upon a Fundamental Change.

     (a) If a Fundamental Change occurs prior to the Final Maturity Date, each
Holder of a Security shall have the right, at the option of the Holder, to
require the Company to repurchase for cash all or any portion of the Securities
of such Holder equal to $1,000 principal amount (or an integral multiple
thereof) at the Fundamental Change Purchase Price, on the date that is not less
than 30 days nor more than 45 days after the date of the Fundamental Change
Company Notice pursuant to subsection 3.01(b) (the "Fundamental Change Purchase
Date").

     (b) On or before the 30th day after the occurrence of a Fundamental Change,
the Company shall mail a written notice of the Fundamental Change and of the
resulting repurchase right to the Trustee, Paying Agent and to each Holder (and
to beneficial owners as required by applicable law) (the "Fundamental Change
Company Notice"). The Fundamental Change Company Notice shall include the form
of a Fundamental Change Purchase Notice to be completed by the Holder and shall
state:

          (1) the events causing such Fundamental Change;

          (2) the date of such Fundamental Change;

          (3) the last date by which the Fundamental Change Purchase Notice must
     be delivered to elect the repurchase option pursuant to this Section 3.01;

          (4) the Fundamental Change Purchase Date;

          (5) the Fundamental Change Purchase Price;

          (6) the Holder's right to require the Company to purchase the
     Securities;

          (7) the name and address of each Paying Agent and Conversion Agent;

          (8) the then effective Conversion Rate and any adjustments to the
     Conversion Rate resulting from such Fundamental Change;

          (9) the procedures that the Holder must follow to exercise rights
     under Article 4 and that Securities as to which a Fundamental Change
     Purchase Notice has been given may be converted into Common Stock pursuant
     to Article 4 of this Indenture only to the extent that the Fundamental
     Change Purchase Notice has been duly withdrawn in accordance with the terms
     of this Indenture;

          (10) the procedures that the Holder must follow to exercise rights
     under this Section 3.01;

          (11) the procedures for withdrawing a Fundamental Change Purchase
     Notice;

          (12) that, unless the Company fails to pay such Fundamental Change
     Purchase Price, Securities covered by any Fundamental Change Purchase
     Notice that is properly given and not


                                       21

<PAGE>

     validly withdrawn will cease to be outstanding and interest and Additional
     Interest, if any, will cease to accrue on and after the Fundamental Change
     Purchase Date; and

          (13) the CUSIP number of the Securities.

At the Company's request, the Trustee shall give such Fundamental Change Company
Notice in the Company's name and at the Company's expense; provided that, in all
cases, the text of such Fundamental Change Company Notice shall be prepared by
the Company. If any of the Securities is in the form of a Global Security, then
the Company shall modify such notice to the extent necessary to accord with the
Applicable Procedures relating to the purchase of Global Securities.

     (c) A Holder may exercise its rights specified in Section 3.01(a) upon
delivery of a written notice (which shall be in substantially the form attached
as Exhibit A under the heading "Fundamental Change Purchase Notice" and which
may be delivered by letter, overnight courier, hand delivery, facsimile
transmission or in any other written form and, in the case of Global Securities,
may be delivered electronically or by other means in accordance with the
Depositary's Applicable Procedures) of the exercise of such rights (a
"Fundamental Change Purchase Notice") to the Company or any Paying Agent at any
time prior to the Fundamental Change Purchase Date, subject to extension to
comply with applicable law.

          (1) The Fundamental Change Purchase Notice shall state: (A) the
     certificate number (if such Security is held other than in global form) of
     the Security which the Holder will deliver to be purchased (or, if the
     Security is held in global form, any other items required to comply with
     the Applicable Procedures), (B) the portion of the principal amount of the
     Security which the Holder will deliver to be purchased and (C) that such
     Security shall be purchased as of the Fundamental Change Purchase Date
     pursuant to the terms and conditions specified in the Securities and in
     this Indenture.

          (2) The delivery of a Security for which a Fundamental Change Purchase
     Notice has been timely delivered to any Paying Agent and not duly withdrawn
     (together with all necessary endorsements) at the office of such Paying
     Agent shall be a condition to the receipt by the Holder of the Fundamental
     Change Purchase Price therefor.

          (3) The Company shall only be obliged to purchase, pursuant to this
     Section 3.01, 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
     purchase of such portion of such Security).

          (4) Notwithstanding anything herein to the contrary, any Holder
     delivering to a Paying Agent the Fundamental Change Purchase Notice
     contemplated by this Section 3.01(c) shall have the right to withdraw such
     Fundamental Change Purchase Notice in whole or in a portion thereof that is
     a principal amount of $1,000 or in an integral multiple thereof at any time
     prior to the close of business on the Business Day prior to the Fundamental
     Change Purchase Date by delivery of a written notice of withdrawal to the
     Paying Agent in accordance with Section 3.02.

          (5) A Paying Agent shall promptly notify the Company of the receipt by
     it of any Fundamental Change Purchase Notice or written withdrawal thereof.

          (6) Anything herein to the contrary notwithstanding, in the case of
     Global Securities, any Fundamental Change Purchase Notice may be delivered
     or withdrawn and such Securities


                                       22

<PAGE>

     may be surrendered or delivered for purchase in accordance with the
     Applicable Procedures as in effect from time to time.

     Section 3.02 Effect of Fundamental Change Purchase Notice.

     (a) Upon receipt by any Paying Agent of a properly completed Fundamental
Change Purchase Notice from a Holder, the Holder of the Security in respect of
which such Fundamental Change Purchase Notice was given shall (unless such
Fundamental Change Purchase Notice is duly withdrawn as specified in Section
3.02(b)) thereafter be entitled to receive the Fundamental Change Purchase Price
with respect to such Security, subject to the absence of an Event of Default, or
a continuation thereof (other than a Default in the payment of the Fundamental
Change Purchase Price). Such Fundamental Change Purchase Price shall be paid to
such Holder promptly following the later of (1) the Fundamental Change Purchase
Date (provided that the conditions in Section 3.01(c) have been satisfied) and
(2) the time of delivery of such Security to a Paying Agent by the Holder
thereof in the manner required by Section 3.01(c). Securities in respect of
which a Fundamental Change Purchase Notice has been given by the Holder thereof
may not be converted into shares of Common Stock pursuant to Article 4 on or
after the date of the delivery of such Fundamental Change Purchase Notice unless
such Fundamental Change Purchase Notice has first been duly withdrawn in
accordance with Section 3.02(b) with respect to the Securities to be converted.

     (b) A Fundamental Change Purchase Notice may be withdrawn by means of a
written notice (which may be delivered by mail, overnight courier, hand
delivery, facsimile transmission or in any other written form and, in the case
of Global Securities, may be delivered electronically or by other means in
accordance with the Applicable Procedures) of withdrawal delivered by the Holder
to a Paying Agent at any time prior to the close of business on the Business Day
immediately prior to the Fundamental Change Purchase Date (unless the Company
shall fail to make the Fundamental Change Purchase Price payments when due in
accordance with Article 3, in which case the withdrawal right shall terminate at
the close of business on the date such failure is cured and such security is
purchased), specifying (1) the principal amount of the Security or portion
thereof (which must be a principal amount of $1,000 or an integral multiple of
$1,000 in excess thereof) with respect to which such notice of withdrawal is
being submitted, (2) if certificated Securities have been issued, the
certificate number of the Security being withdrawn in whole or in withdrawable
part (or if the Securities are not certificated, such written notice must comply
with the Applicable Procedures) and (3) the portion of the principal amount of
the Security that will remain subject to the Fundamental Change Purchase Notice,
which portion must be a principal amount of $1,000 or an integral multiple
thereof.

     Section 3.03 Deposit of Fundamental Change Purchase Price.

     (a) Before 12:00 p.m. (noon) New York City time on the applicable
Fundamental Change Purchase Date, the Company shall deposit with the Trustee or
with a 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) an amount of money (in immediately available funds), sufficient to pay the
aggregate Fundamental Change Purchase Price of all the Securities or portions
thereof that are to be purchased as of such Fundamental Change Purchase Date.

     (b) If a Paying Agent or the Trustee holds, in accordance with the terms
hereof, money sufficient to pay the Fundamental Change Purchase Price of any
Security for which a Fundamental Change Purchase Notice has been tendered and
not duly withdrawn in accordance with this Indenture then, on the Business Day
following the Fundamental Change Purchase Date, such Security will cease to be
outstanding, whether or not the Security is delivered to the Paying Agent or the
Trustee, and interest and Additional Interest, if any, shall cease to accrue,
and the rights of the Holder in respect of the Security


                                       23

<PAGE>

shall terminate (other than the right to receive the Fundamental Change Purchase
Price as aforesaid). The Company shall publicly announce in accordance with
applicable law the principal amount of Securities repurchased on or as soon as
practicable after the Fundamental Change Purchase Date.

     (c) The Paying Agent will promptly return to the respective Holders thereof
any Securities with respect to which a Fundamental Change Purchase Notice has
been duly withdrawn in compliance with this Indenture.

     (d) If a Fundamental Change Purchase Date falls after a Regular Record Date
and on or before the related Interest Payment Date, then interest on the
Securities payable on such Interest Payment Date will be payable to the Holders
in whose names the Securities are registered at the close of business on such
Regular Record Date.

     Section 3.04 Repayment to The Company.

     To the extent that the aggregate amount of cash deposited by the Company
pursuant to Section 3.03 exceeds the aggregate Fundamental Change Purchase Price
of the Securities or portions thereof that the Company is obligated to purchase,
then promptly after the Fundamental Change Purchase Date the Trustee or a Paying
Agent, as the case may be, shall return any such excess cash to the Company.

     Section 3.05 Securities Purchased in Part.

     Any Security that is to be purchased only in part shall be surrendered at
the office of a Paying Agent, and promptly after the Fundamental Change Purchase
Date, 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 such authorized denomination or denominations as may be requested
by such Holder (which must be equal to $1,000 principal amount or any integral
thereof), in aggregate principal amount equal to, and in exchange for, the
portion of the principal amount of the Security so surrendered that is not
purchased.

     Section 3.06 Compliance with Securities Laws upon Purchase of Securities.

     In connection with any offer to purchase Securities under Section 3.01, the
Company shall (a) comply with Rule 13e-4 and Rule 14e-1 (or any successor to
either such Rule), and any other tender offer rules, if applicable, under the
Exchange Act, (b) file the related Schedule TO (or any successor or similar
schedule, form or report) if required under the Exchange Act, and (c) otherwise
comply with all federal and state securities laws in connection with such offer
to purchase or purchase of Securities, all so as to permit the rights of the
Holders and obligations of the Company under Sections 3.01 through 3.04 to be
exercised in the time and in the manner specified therein. To the extent that
compliance with any such laws, rules and regulations would result in a conflict
with any of the terms hereof, this Indenture is hereby modified to the extent
required for the Company to comply with such laws, rules and regulations.


                                       24

<PAGE>

     Section 3.07 Purchase of Securities in Open Market.

     The Company (a) on or prior to the date that is two years from the latest
issuance of any Securities and in accordance with Section 2.11, shall surrender
any Security purchased by the Company pursuant to this Article 3 to the Trustee
for cancellation, and (b) after such date and in accordance with Section 2.11,
may surrender such Security to the Trustee for cancellation. Any securities
surrendered to the Trustee for cancellation may not be reissued or resold by the
Company and will be canceled promptly in accordance with Section 2.11. The
Company may repurchase Securities in the open market, by tender at any price or
by negotiated transactions and such Securities may be reissued or resold, to the
extent permitted by applicable law, or may be surrendered to the Trustee for
cancellation.


                                       25

<PAGE>

                                    ARTICLE 4

                                   CONVERSION

     Section 4.01 Conversion Privilege and Conversion Rate.

     (a) Subject to the obligation and the right of the Company to pay some or
all of the conversion consideration in cash in accordance with Section 4.13, if
the Company has not made a Physical Settlement Election, and upon compliance
with the provisions of this Article 4, at the option of the Holder thereof, any
Security or portion thereof that is an integral multiple of $1,000 principal
amount may be converted into fully paid and nonassessable shares (calculated as
to each conversion to the nearest 1/100th of a share) of Common Stock prior to
the close of business on the Business Day immediately preceding the Final
Maturity Date or such earlier date set forth in this Article 4, unless
previously purchased by the Company at the Holder's option upon the occurrence
of a Fundamental Change, at the Conversion Rate in effect at such time,
determined as hereinafter provided and subject to the adjustments described
below, only under the following circumstances:

          (1) during any calendar quarter beginning after June 30, 2007, and
     only during such calendar quarter, if, as of the last day of the
     immediately preceding calendar quarter, the Closing Price per share of the
     Common Stock for at least 20 Trading Days in the period of the 30
     consecutive Trading Days ending on the last Trading Day of such preceding
     calendar quarter was more than 120% of the Conversion Price (the
     "Conversion Trigger Price");

          (2) if the Company distributes to all holders of Common Stock rights
     (including rights under a stockholder rights agreement) or warrants
     entitling them to purchase, for a period expiring within 45 days of the
     date of issuance, Common Stock at less than the Current Market Price of the
     Common Stock on the day of issuance;

          (3) if the Company distributes to all holders of Common Stock, cash,
     assets, debt securities or rights to purchase the Company's securities,
     which distribution has a per share value exceeding 7.5% of the Closing
     Price of the Common Stock on the Trading Day preceding the declaration date
     for such distribution;

          (4) if a Fundamental Change occurs;

          (5) at any time during the period beginning on February 15, 2012 and
     ending at the close of business on the Business Day immediately preceding
     the Final Maturity Date; or

          (6) during any five Business Day period after any five consecutive
     Trading Day period in which the Trading Price per $1,000 principal amount
     of Securities, as determined following a request by a Holder in accordance
     with the procedures described below in Section 4.01(e)(ii), for each day of
     that period was less than 98% of the product of the Closing Price of the
     Common Stock for each day in that period and the Conversion Rate.

     (b) In the case of a distribution contemplated by clauses (2) and (3) of
Section 4.01(a), the Company shall notify Holders at least 20 days prior to the
ex-dividend date for such distribution (the "Distribution Notice"); provided
that if the Company distributes rights pursuant to a stockholder rights
agreement, it will notify the Holders of the Securities on the Business Day
after the Company is required to give notice generally to its stockholders
pursuant to such stockholder rights agreement if such date is less than 20 days
prior to the date of such distribution. Once the Company has given the
Distribution Notice, Holders may surrender their Securities for conversion at
any time until the earlier of the close of


                                       26

<PAGE>

business on the last Business Day preceding the ex-dividend date or the
Company's announcement that such distribution will not take place. In the event
of a distribution contemplated by clauses (2) and (3) of Section 4.01(a),
Holders may not convert the Securities if the Holders will otherwise participate
in such distribution without converting their Securities. The Company will
provide written notice to the Conversion Agent as soon as reasonably practicable
of any anticipated or actual event or transaction that will cause or causes the
Securities to become convertible pursuant to clauses (2) or (3) of Section
4.01(a).

     (c) [Intentionally Omitted]

     (d) In the case of a transaction contemplated by clause (4) of section
4.01(a), the Company will notify the Holders and Trustee at least 10 Trading
Days prior to the anticipated Fundamental Change Effective Date of any
Fundamental Change that the Company knows or reasonably should know will occur.
If the Company does not know, and should not reasonably know, that a Fundamental
Change will occur until a date that is within 10 Trading Days before the
anticipated Fundamental Change Effective Date, the Company will notify the
Holders and the Trustee promptly after the Company has knowledge of such
Fundamental Change. Holders may surrender Securities for conversion at any time
beginning 10 Trading Days before the anticipated Fundamental Change Effective
Date of a Fundamental Change and until the close of business on the Business Day
immediately preceding the Fundamental Change Purchase Date.

     (e) (i) For each calendar quarter of the Company, beginning with the
calendar quarter ending June 30, 2007, the Conversion Agent, on behalf of the
Company, will determine, on the first Business Day following the last Trading
Day of such calendar quarter, whether the Securities are convertible pursuant to
clause (1) of Section 4.01(a), and, if so, will notify the Trustee and the
Company in writing. Upon request of the Conversion Agent, the Company shall
provide, or cause to be provided to, the Conversion Agent the Closing Price per
share of Common Stock for the 30 consecutive Trading Days ending on the last
Trading Day of the preceding calendar quarter.

          (ii) The Bid Solicitation Agent shall have no obligation to determine
the Trading Price of the Securities and whether the Securities are convertible
pursuant to clause (6) of Section 4.01(a) unless the Company has requested such
determination in writing; and the Company shall have no obligation to make such
request unless a Holder of Securities provides the Company with reasonable
evidence that the Trading Price per $1,000 principal amount of Securities would
be less than 98% of the product of the Closing Price of the Common Stock and the
Conversion Rate. At such time, the Company shall instruct the Bid Solicitation
Agent to determine the Trading Price of the Securities beginning on the next
Trading Day and on each successive Trading Day until the Trading Price per
$1,000 principal amount of the Securities is greater than 98% of the product of
the Closing Price of the Common Stock and the Conversion Rate.

     (f) The conversion rights pursuant to this Article 4 shall commence on the
initial issuance date of the Securities and expire at the close of business on
the Business Day immediately preceding the Final Maturity Date, but shall be
exercisable only during the time periods specified with respect to each
circumstance pursuant to which the Securities become convertible, subject, in
the case of conversion of any Global Security, to any Applicable Procedures. If
a Security is convertible as a result of a Fundamental Change, such conversion
right shall commence and terminate as set forth in Section 4.01(d). Securities
in respect of which a Fundamental Change Purchase Notice has been delivered may
not be surrendered for conversion pursuant to this Article 4 prior to a due
withdrawal of such Fundamental Change Notice in accordance with the provisions
of Article 3.

     (g) Provisions of this Indenture that apply to conversion of all of a
Security also apply to conversion of a portion of a Security.


                                       27

<PAGE>

     (h) A Holder of Securities is not entitled to any rights of a holder of
Common Stock until such Holder has converted its Securities into Common Stock,
and only to the extent such Securities are deemed to have been converted into
Common Stock pursuant to this Article 4.

     (i) The Conversion Rate shall be adjusted in certain instances as provided
in Sections 4.01(j) and Section 4.06.

     (j) If there shall have occurred a Fundamental Change, then the Conversion
Rate per $1,000 principal amount of Securities otherwise in effect in respect of
Securities that are converted during the period beginning 10 Trading Days before
the anticipated Fundamental Change Effective Date and ending at the close of
business on the Business Day immediately preceding the Fundamental Change
Purchase Date shall be increased by the amount, if any, determined by reference
to the table below, based on the Fundamental Change Effective Date and the Stock
Price of such Fundamental Change; provided that if the Stock Price or
Fundamental Change Effective Date are not set forth on the table: (i) if the
actual Stock Price on the Fundamental Change Effective Date is between two Stock
Prices on the table or the actual Fundamental Change Effective Date is between
two Fundamental Change Effective Dates on the table, the amount of the
Conversion Rate adjustment will be determined by a straight-line interpolation
between the adjustment amounts set forth for the two Stock Prices and the two
Fundamental Change Effective Dates on the table based on a 365-day year, as
applicable, (ii) if the Stock Price on the Fundamental Change Effective Date
exceeds $120.00 per share, subject to adjustment as set forth herein, no
adjustment to the applicable Conversion Rate will be made, and (iii) if the
Stock Price on the Fundamental Change Effective Date is less than $32.93 per
share, subject to adjustment as set forth herein, no adjustment to the
applicable Conversion Rate will be made. If all holders of the Common Stock
receive cash, and only cash, in the Fundamental Change, the Stock Price shall be
the cash amount paid per share of the Common Stock in connection with the
Fundamental Change. Otherwise, the Stock Price shall be equal to the average
Closing Prices of the Common Stock for each of the 10 Trading Days immediately
preceding, but not including, the applicable Fundamental Change Effective Date.

     The following table shows the amount, if any, by which the applicable
Conversion Rate will increase for each hypothetical Stock Price and Fundamental
Change Effective Date set forth below:

 MAKE WHOLE PREMIUM UPON A FUNDAMENTAL CHANGE (INCREASE IN APPLICABLE CONVERSION
                                      RATE)

<TABLE>
<CAPTION>
STOCK PRICE ON   MARCH 19,   MARCH 15,   MARCH 15,   MARCH 15,   MARCH 15,   MARCH 15,
EFFECTIVE DATE      2007        2008        2009        2010        2011        2012
--------------   ---------   ---------   ---------   ---------   ---------   ---------
<S>              <C>         <C>         <C>         <C>         <C>         <C>
    $ 32.93        9.0569      9.0569      9.0569      9.0569      9.0569      9.0569
    $ 35.00        8.0727      7.9278      7.7130      7.4272      7.2609      7.2609
    $ 40.00        6.2394      5.9989      5.6621      5.2033      4.5095      3.6895
    $ 45.00        4.9449      4.6561      4.2607      3.7227      2.8943      0.9117
    $ 50.00        4.0057      3.6971      3.2802      2.7238      1.8796      0.0000
    $ 60.00        2.7749      2.4699      2.0739      1.5656      0.8592      0.0000
    $ 70.00        2.0350      1.7603      1.4131      0.9920      0.4655      0.0000
    $ 80.00        1.5609      1.3213      1.0274      0.6881      0.3023      0.0000
    $120.00        0.7154      0.5836      0.4349      0.2887      0.1455      0.0000
</TABLE>

     The Stock Prices set forth in the first column of the table above will be
adjusted as of any date on which the Conversion Rate of the Securities is
adjusted, other than as a result of an adjustment of the Conversion Rate by
virtue of the provisions of this Section 4.01(j). The adjusted Stock Prices will
equal the Stock Prices applicable immediately prior to such adjustment
multiplied by a fraction, the numerator of which is the Conversion Rate
immediately prior to the adjustment giving rise to the Stock Price adjustment
and the denominator of which is the Conversion Rate as so adjusted. The
Conversion Rate


                                       28

<PAGE>

adjustment amounts set forth in the table above will be adjusted in the same
manner as the Conversion Rate as set forth in Section 4.06 hereof.

     Notwithstanding the foregoing paragraph, in no event will the Conversion
Rate exceed 30.3674 per $1,000 principal amount of Securities, subject to
adjustment in the manner set forth in clauses (1) through (4) of Section 4.06(a)
hereof.

     (k) Except as set forth in Section 4.02(c), by delivering the amount of
cash and/or the number of shares of Common Stock issuable on conversion to the
Trustee, as applicable, the Company will be deemed to have satisfied its
obligation to pay the principal amount of the Securities so converted and its
obligation to pay accrued and unpaid interest, and Additional Interest if any,
attributable to the period from the most recent Interest Payment Date through
the Conversion Date (which amount will be deemed paid in full rather than
cancelled, extinguished or forfeited).

     Section 4.02 Conversion Procedure.

     (a) To convert a Security, a Holder must (1) complete and manually sign the
conversion notice on the back of the Security and deliver such notice to a
Conversion Agent, (2) surrender the Security to a Conversion Agent, (3) furnish
appropriate endorsements and transfer documents if required by a Registrar or a
Conversion Agent, and (4) pay all transfer or similar taxes, if required
pursuant to Section 4.04. The date on which the Holder satisfies all of those
requirements is the "Conversion Date." Upon the conversion of a Security, the
Company will pay the cash and deliver the shares of Common Stock, as applicable,
as promptly as practicable after the expiration of the Conversion Reference
Period, but in no event later than the fifth Business Day after such expiration.
Anything herein to the contrary notwithstanding, in the case of Global
Securities, conversion notices may be delivered and such Securities may be
surrendered for conversion in accordance with the Applicable Procedures as in
effect from time to time.

     (b) The person in whose name the shares of Common Stock are issuable upon
conversion shall be deemed to be a holder of record of such Common Stock on the
later of (i) the Conversion Date, (ii) the expiration of the period in which the
Company may elect to deliver cash in lieu of shares of common stock if the
Company has not made a Physical Settlement Election, or (iii) if the Company has
not made a Physical Settlement Election and elects to deliver cash in lieu of
some, but not all, of such shares of Common Stock, the date on which the amount
of cash issuable per Security has been determined; provided, however, that no
surrender of a Security on any Conversion 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 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; provided further that such conversion shall be at
the Conversion Rate in effect on the Conversion Date 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. Except as set forth in this
Indenture, no payment or adjustment will be made for dividends or distributions
declared or made on shares of Common Stock issued upon conversion of a Security
prior to the issuance of such shares.

     (c) Holders of Securities surrendered for conversion (in whole or in part)
during the period from the close of business on any Regular Record Date to the
opening of business on the next succeeding Interest Payment Date will receive
the semi-annual interest payable on such Securities on the corresponding
Interest Payment Date notwithstanding the conversion. Upon surrender of any such
Securities for conversion, unless such Securities have been surrendered for
conversion following the


                                       29

<PAGE>

regular record date immediately preceding the final interest payment date (March
15, 2012), such Securities shall also be accompanied by payment in funds
acceptable to the Company of an amount equal to the interest payable on such
corresponding Interest Payment Date. Except as otherwise provided in this
Section 4.02(c), no payment or adjustment will be made for accrued interest on a
converted Security.

     (d) Subject to Section 4.02(c), nothing in this Section shall affect the
right of a Holder in whose name any Security is registered at the close of
business on a Regular Record Date to receive the interest payable on such
Security on the related Interest Payment Date in accordance with the terms of
this Indenture, the Securities and the Registration Rights Agreement. If a
Holder converts more than one Security at the same time, the number of shares of
Common Stock issuable upon the conversion and any amount of cash to be paid, as
applicable (and the amount of any cash in lieu of fractional shares pursuant to
Section 4.03), shall be based on the aggregate principal amount of all
Securities so converted.

     (e) In the case of any Security which is converted in part only, upon such
conversion the Company shall execute and the Trustee shall authenticate and
deliver to the Holder thereof, without service charge, a new Security or
Securities of authorized denominations in an aggregate principal amount equal
to, and in exchange for, the unconverted portion of the principal amount of such
Security. A Security may be converted in part, but only if the principal amount
of such part is an integral multiple of $1,000 and the principal amount of such
Security to remain outstanding after such conversion is equal to $1,000 or any
integral multiple of $1,000 in excess thereof.

     (f) Upon the Company's determination that a Holder is or will be entitled
to convert their Securities into shares of Common Stock pursuant to this Article
4, the Company will promptly after making such determination issue a press
release and use its reasonable efforts to post such information on the Company's
website or otherwise publicly disclose such information.

     Section 4.03 Fractional Shares.

     Notwithstanding anything contained herein to the contrary, the Company will
not issue fractional shares of Common Stock upon conversion of Securities. If
more than one Security shall be surrendered for conversion at one time by the
same Holder, the number of full shares that shall be issuable upon conversion
shall be computed on the basis of the aggregate principal amount of the
Securities (or specified portions thereof to the extent permitted hereby) so
surrendered. In lieu of any fractional shares, the Company will pay an amount in
cash for the current market value of the fractional shares. The current market
value of a fractional share shall be determined (calculated to the nearest
1/100th of a share) by multiplying the arithmetic average of the Volume Weighted
Average Price of the Common Stock for each of the fifteen consecutive Trading
Days of the Conversion Reference Period (or if the Company has made a Physical
Settlement Election, the Trading Day immediately prior to the conversion of the
Security) by such fractional share and rounding the product to the nearest whole
cent.


                                       30

<PAGE>

     Section 4.04 Taxes on Conversion.

     If a Holder converts a Security, the Company shall pay any transfer, stamp
or similar taxes or duties related to the issue or delivery of shares of Common
Stock upon such conversion. The Company shall also pay any such tax with respect
to cash received in lieu of fractional shares. 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
certificate 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 regulation.

     Section 4.05 Company to Provide Stock.

     (a) 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 all outstanding Securities into shares of Common Stock.

     (b) All shares of Common Stock delivered upon conversion of the Securities
shall be newly issued shares, shall be duly authorized, validly issued, fully
paid and nonassessable and shall be free from preemptive or similar rights and
free of any lien or adverse claim as the result of any action by the Company.

     (c) The Company will endeavor promptly to comply with all federal and state
securities laws regulating the offer and delivery of shares of Common Stock upon
conversion of Securities.

     Section 4.06 Adjustment of Conversion Rate.

     (a) The Conversion Rate shall be adjusted from time to time by the Company
as follows:

          (1) If the Company shall pay a dividend or make a distribution to all
     holders of outstanding Common Stock in shares of Common Stock, the
     Conversion Rate in effect immediately prior to the record date for the
     determination of stockholders entitled to receive such dividend or other
     distribution shall be increased so that the same shall equal the rate
     determined by multiplying the Conversion Rate in effect immediately prior
     to such record date by a fraction of which the numerator shall be the sum
     of the number of shares of Common Stock outstanding at the close of
     business on such record date plus the total number of shares of Common
     Stock constituting such dividend or other distribution and of which the
     denominator shall be the number of shares of Common Stock outstanding at
     the close of business on such record date. Such adjustment shall be made
     successively whenever any such dividend or distribution is made and shall
     become effective immediately after such record date. For the purpose of
     this clause (1), the number of shares of Common Stock at any time
     outstanding shall not include shares held in the treasury of the Company.
     The Company will not pay any dividend or make any distribution on Common
     Stock held in the treasury of the Company. If any dividend or distribution
     of the type described in this clause is declared but not so paid or made,
     the Conversion Rate shall again be adjusted to the Conversion Rate that
     would then be in effect if such dividend or distribution had not been
     declared.

          (2) If the Company shall subdivide its outstanding Common Stock into a
     greater number of shares, or combine its outstanding Common Stock into a
     smaller number of shares, the Conversion Rate in effect immediately prior
     to the day upon which such subdivision or


                                       31

<PAGE>

     combination becomes effective shall be, in the case of a subdivision of
     Common Stock, proportionately increased and, in the case of a combination
     of Common Stock, proportionately reduced. Such adjustment shall be made
     successively whenever any such subdivision or combination of the Common
     Stock occurs and shall become effective immediately after the date upon
     which such subdivision or combination becomes effective.

          (3) If the Company shall issue rights (other than the Rights (as
     defined below) contemplated in Section 4.06(a)(5) below) or warrants to all
     holders of its outstanding Common Stock entitling them (for a period
     expiring within 45 days after such issuance) to subscribe for or purchase
     shares of Common Stock (or securities convertible into Common Stock) at a
     price per share (or having a conversion price per share) less than the
     Current Market Price per share of Common Stock (as determined in accordance
     with clause (9) of this Section 4.06(a)) on 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 rate determined by multiplying the
     Conversion Rate in effect immediately prior to such record date by a
     fraction of which the numerator shall be the number of shares of Common
     Stock outstanding at the close of business on such record date plus the
     number of additional shares of Common Stock that such rights or warrants
     entitle holders thereof to subscribe for or purchase (or into which such
     convertible securities are convertible) and of which the denominator shall
     be the number of shares of Common Stock outstanding at the close of
     business on such record date plus the number of shares which the aggregate
     offering price of the total number of shares of Common Stock so offered for
     subscription or purchase (or the aggregate conversion price of the
     convertible securities so offered for subscription or purchase, which shall
     be determined by multiplying the number of shares of Common Stock issuable
     upon conversion of such convertible securities by the conversion price per
     share of Common Stock pursuant to the terms of such convertible securities)
     would purchase at the Current Market Price per share of Common Stock on
     such record date. Such adjustment shall be made successively whenever any
     such rights or warrants are issued, and shall become effective immediately
     after such record date. To the extent that shares of Common Stock (or
     securities convertible into Common Stock) are not delivered after the
     expiration of such rights or warrants, the Conversion Rate shall be
     readjusted to the Conversion Rate that 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 (or
     securities convertible into 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 that would then be in effect if the
     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 stockholders to subscribe for or purchase shares of
     Common Stock at a price less than the Current Market Price per share of
     Common Stock and in determining the aggregate offering price of the total
     number of shares of Common Stock so offered, there shall be taken into
     account any consideration received by the Company for such rights or
     warrants and any amount payable on exercise or conversion thereof, the
     value of such consideration, if other than cash, to be determined by the
     Board of Directors.

          (4) If the Company shall make a dividend or other distribution to all
     holders of its Common Stock of Capital Stock, other than Common Stock, or
     evidences of indebtedness or other assets of the Company (excluding (x) any
     issuance of rights or warrants for which an adjustment was made pursuant to
     Section 4.06(a)(3), (y) dividends or distributions in connection with a
     reclassification, change, consolidation, merger, combination, liquidation,
     dissolution, winding up, sale or conveyance resulting in a change in the
     conversion consideration, or pursuant to any shareholder rights plan or (z)
     any dividend or distribution paid exclusively in cash for which an
     adjustment was made pursuant to Section 4.06(a)(6)) (the "Distributed
     Securities"), then


                                       32

<PAGE>

     in each such case (unless the Company distributes such Distributed
     Securities for distribution to the Holders of Securities on such dividend
     or distribution date as if each Holder had converted such Security into
     Common Stock immediately prior to the record date with respect to such
     distribution) the Conversion Rate in effect immediately prior to the record
     date fixed for the determination of shareholders entitled to receive such
     dividend or distribution shall be adjusted so that the same shall equal the
     rate determined by multiplying the Conversion Rate in effect immediately
     prior to such record date by a fraction of which the numerator shall be the
     Current Market Price per share of the Common Stock on such record date and
     of which the denominator shall be the Current Market Price per share on
     such record date less the fair market value (as determined in good faith by
     the Board of Directors, whose determination shall be conclusive evidence of
     such fair market value and which shall be evidenced by an Officers'
     Certificate delivered to the Trustee) on such record date of the portion of
     the Distributed Securities so distributed applicable to one share of Common
     Stock (determined on the basis of the number of shares of Common Stock
     outstanding at the close of business on such record date). Such adjustment
     shall be made successively whenever any such distribution is made and shall
     become effective immediately after the record date for the determination of
     shareholders entitled to receive such distribution. In the event that such
     dividend or distribution is not so paid or made, the Conversion Rate shall
     again be adjusted to be the Conversion Rate that would then be in effect if
     such dividend or distribution had not been declared.

     If the 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 Current Market Price per share of the
     Common Stock on such record date, in lieu of the foregoing adjustment,
     adequate provision shall be made so that each holder of a Security shall
     have the right to receive upon conversion the amount of Distributed
     Securities so distributed that such Holder would have received had such
     Holder converted each Security on such record date. If the Board of
     Directors determines the fair market value of any distribution for purposes
     of this Section 4.06(a)(4) 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 Current Market
     Price of the Common Stock.

     Notwithstanding the foregoing, if the securities distributed by the Company
     to all holders of its Common Stock consist of Capital Stock of, or similar
     equity interests in, a Subsidiary or other business unit of the Company
     (the "Spinoff Securities"), the Conversion Rate shall be adjusted, unless
     the Company makes an equivalent distribution to the Holders of the
     Securities, so that the same shall be equal to the rate determined by
     multiplying the Conversion Rate in effect on the record date fixed for the
     determination of shareholders entitled to receive such distribution by a
     fraction, the numerator of which shall be the sum of (A) the average
     Closing Price of one share of Common Stock over the ten consecutive Trading
     Day period (the "Spinoff Valuation Period") commencing on and including the
     fifth Trading Day after the date on which ex-dividend trading commences for
     such distribution on the Nasdaq Global Market or such other U.S. national
     or regional exchange or market on which the Common Stock is then listed or
     quoted and (B) the average of the Closing Prices over the Spinoff Valuation
     Period of the Spinoff Securities multiplied by the number of Spinoff
     Securities distributed in respect of one share of Common Stock and the
     denominator of which shall be the average Closing Price of one share of
     Common Stock over the Spinoff Valuation Period, such adjustment to become
     effective immediately prior to the opening of business on the fifteenth
     Trading Day after the date on which ex-dividend trading commences;
     provided, however, that the Company may in lieu of the foregoing adjustment
     elect to make adequate provision so that each Holder of Securities shall
     have the right to receive upon conversion thereof the amount of such
     Spinoff Securities that such Holder of


                                       33

<PAGE>

     Securities would have received if such Securities had been converted on the
     record date with respect to such distribution.

          (5) With respect to any rights or warrants (the "Rights") that may be
     issued or distributed pursuant to any rights plan that the Company
     implements after the date of this Indenture (a "Rights Plan"), or if the
     Company's current Rights Plan is still in effect, in lieu of any adjustment
     required by any other provision of this Section 4.06 upon conversion of the
     Securities into Common Stock, to the extent that such Rights Plan is in
     effect upon such conversion, the Holders of Securities will receive, with
     respect to the shares of Common Stock issued upon conversion, the Rights
     described therein (whether or not the Rights have separated from the Common
     Stock at the time of conversion), subject to the limitations set forth in
     and in accordance with any such Rights Plan; provided that in the case of
     the Company's current Rights Plan or a future Rights Plan to the extent
     applicable, if, at the time of conversion, however, the Rights have
     separated from the shares of Common Stock in accordance with the provisions
     of the Rights Plan so that Holders would not be entitled to receive any
     rights in respect of the shares of Common Stock issuable upon conversion of
     the Securities as a result of the timing of the Conversion Date, the
     Conversion Rate will be adjusted as if the Company distributed to all
     holders of Common Stock Distributed Securities constituting such rights as
     provided in the first paragraph of clause (4) of this Section 4.06(a),
     subject to appropriate readjustment in the event of the invalidation,
     termination, repurchase or redemption of the Rights. Any distribution of
     rights or warrants pursuant to a Rights Plan complying with the
     requirements set forth in the immediately preceding sentence of this
     paragraph shall not constitute a distribution of rights or warrants
     pursuant to this Section 4.06(a). Other than as specified in this clause
     (5) of this Section 4.06(a), there will not be any adjustment to the
     Conversion Rate as the result of the issuance of any Rights, the
     distribution of separate certificates representing such Rights, the
     exercise or redemption of such Rights in accordance with any Rights Plan or
     the termination or invalidation of any Rights.

          (6) If the Company shall, by dividend or otherwise, at any time
     distribute (a "Triggering Distribution") to all holders of its Common Stock
     a payment consisting exclusively of cash (excluding any dividend or
     distribution in connection with the liquidation, dissolution or winding up
     of the Company, whether voluntary or involuntary) the Conversion Rate shall
     be increased so that the same shall equal the rate determined by
     multiplying such Conversion Rate in effect immediately prior to the close
     of business on the record date for such Triggering Distribution (a
     "Determination Date") by a fraction of which the numerator shall be such
     Current Market Price per share of the Common Stock on the Determination
     Date and the denominator of which shall be the Current Market Price per
     share of the Common Stock on the Determination Date less the amount of such
     cash dividend or distribution applicable to one share of Common Stock
     (determined on the basis of the number of shares of Common Stock
     outstanding at the close of business on the Determination Date), such
     increase to become effective immediately prior to the opening of business
     on the day following the date on which the Triggering Distribution is paid.
     If the amount of cash dividend or distribution applicable to one share of
     Common Stock is equal to or greater than the Current Market Price per share
     of the Common Stock on the Determination Date, in lieu of the foregoing
     adjustment, adequate provision shall be made so that each Holder of a
     Security shall have the right to receive upon conversion the amount of cash
     so distributed that such Holder would have received had such Holder
     converted each Security on such Determination Date. In the event that such
     dividend or distribution is not so paid or made, the Conversion Rate shall
     again be adjusted to be the Conversion Rate that would then be in effect if
     such divided or distribution had not been declared.


                                       34

<PAGE>

          (7) If any tender offer made by the Company or any of its Subsidiaries
     for all or any portion of Common Stock shall expire, then, if the tender
     offer shall require the payment to shareholders of consideration per share
     of Common Stock having a fair market value (determined as provided below)
     that exceeds the Closing Price per share of Common Stock on the Trading Day
     next succeeding the last date (the "Expiration Date") tenders could have
     been made pursuant to such tender offer (as it may be amended) (the last
     time at which such tenders could have been made on the Expiration Date is
     hereinafter sometimes called the "Expiration Time"), the Conversion Rate
     shall be increased so that the same shall equal the rate determined by
     multiplying the Conversion Rate in effect immediately prior to the close of
     business on the Expiration Date by a fraction of which the numerator shall
     be the sum of (A) the fair market value of the aggregate consideration (the
     fair market value as determined in good faith by the Board of Directors,
     whose determination shall be conclusive evidence of such fair market value
     and which shall be evidenced by an Officers' Certificate delivered to the
     Trustee) payable to shareholders based on the acceptance (up to any maximum
     specified in the terms of the tender offer) of all shares validly tendered
     and not duly withdrawn as of the Expiration Time (the shares deemed so
     accepted, up to any such maximum, being referred to as the "Purchased
     Shares") and (B) the product of the number of shares of Common Stock
     outstanding (less any Purchased Shares and excluding any shares held in the
     treasury of the Company) at the Expiration Time and the Closing Price per
     share of Common Stock on the Trading Day next succeeding the Expiration
     Date and the denominator of which shall be the product of the number of
     shares of Common Stock outstanding (including Purchased Shares but
     excluding any shares held in the treasury of the Company) at the Expiration
     Time multiplied by the Closing Price per share of the Common Stock on the
     Trading Day next succeeding the Expiration Date, such increase to become
     effective immediately prior to the opening of business on the day following
     the Expiration Date. In the event that the Company is obligated to purchase
     shares pursuant to any such tender offer, but the Company is permanently
     prevented by applicable law from effecting any or all such purchases or any
     or all such purchases are rescinded, the Conversion Rate shall again be
     adjusted to be the Conversion Rate which would have been in effect based
     upon the number of shares actually purchased, if any. If the application of
     this clause (7) of Section 4.06(a) to any tender offer would result in a
     decrease in the Conversion Rate, no adjustment shall be made for such
     tender offer under this clause (7).

          (8) For purposes of this Section 4.06, the term "tender offer" shall
     mean and include both tender offers and exchange offers, all references to
     "purchases" of shares in tender offers (and all similar references) shall
     mean and include both the purchase of shares in tender offers and the
     acquisition of shares pursuant to exchange offers, and all references to
     "tendered shares" (and all similar references) shall mean and include
     shares tendered in both tender offers and exchange offers.

          (9) For purposes of any computation under Section 4.01 or this Section
     4.06, "Current Market Price" shall mean the average of the daily Closing
     Prices per share of Common Stock for each of the ten consecutive Trading
     Days immediately prior to the date in question; provided, however, that if

               (A) the "ex" date (as hereinafter defined) for any event (other
          than the issuance or distribution requiring such computation) that
          requires an adjustment to the Conversion Rate pursuant to Section
          4.06(a) (1), (2), (3), (4), (5), (6) or (7) occurs during such ten
          consecutive Trading Days, the Closing Price for each Trading Day prior
          to the "ex" date for such other event shall be adjusted by dividing
          such Closing Price by the same fraction by which the Conversion Rate
          is so required to be adjusted as a result of such other event;


                                       35

<PAGE>

               (B) the "ex" date for any event (other than the issuance or
          distribution requiring such computation) that requires an adjustment
          to the Conversion Rate pursuant to Section 4.06(a) (1), (2), (3), (4),
          (5), (6) or (7) occurs on or after the "ex" date for the issuance or
          distribution requiring such computation and prior to the day in
          question, the Closing Price for each Trading Day on and after the "ex"
          date for such other event shall be adjusted by dividing such Closing
          Price by the reciprocal of the fraction by which the Conversion Rate
          is so required to be adjusted as a result of such other event; and

               (C) the "ex" date for the issuance or distribution requiring such
          computation is prior to the day in question, after taking into account
          any adjustment required pursuant to the immediately preceding clause
          (A) or (B) of this Section 4.06(a)(9), the Closing Price for each
          Trading Day on or after such "ex" date shall be adjusted by adding
          thereto the amount of any cash and the fair market value (as
          determined in good faith by the Board of Directors in a manner
          consistent with any determination of such value for purposes of
          Section 4.06(a)(4) or (7), whose determination shall be conclusive and
          set forth in a Board Resolution) of the evidences of indebtedness,
          shares of capital stock or assets being distributed applicable to one
          share of Common Stock as of the close of business on the day before
          such "ex" date.

     For purposes of any computation under Section 4.06(a)(7), if the "ex" date
     for any event (other than the tender offer that is the subject of the
     adjustment pursuant to Section 4.06(a)(7)) that requires an adjustment to
     the Conversion Rate pursuant to Section 4.06(a)(1), (2), (3), (4), (5) or
     (6) occurs on the date of the Expiration Time for the tender or exchange
     offer requiring such computation or on the Trading Day next following the
     Expiration Time, the Closing Price for each Trading Day on and after the
     "ex" date for such other event shall be adjusted by dividing such Closing
     Price by the reciprocal of the fraction by which the Conversion Rate is so
     required to be adjusted as a result of such other event. For purposes of
     this Section 4.06(a)(9) the term "ex" date, when used:

               (D) with respect to any issuance or distribution, means the first
          date on which the Common Stock trades regular way on the relevant
          exchange or in the relevant market from which the Closing Price was
          obtained without the right to receive such issuance or distribution;

               (E) with respect to any subdivision or combination of shares of
          Common Stock, means the first date on which the Common Stock trades
          regular way on such exchange or in such market after the time at which
          such subdivision or combination becomes effective, and

               (F) with respect to any tender or exchange offer, means the first
          date on which the Common Stock trades regular way on such exchange or
          in such market after the Expiration Time of such offer.

     Notwithstanding the foregoing, whenever successive adjustments to the
     Conversion Rate are called for pursuant to this Section 4.06, such
     adjustments shall be made to the Current Market Price as may be necessary
     or appropriate to effectuate the intent of this Section 4.06 and to avoid
     unjust or inequitable results as determined in good faith by the Board of
     Directors.

     (b) In any case in which this Section 4.06 shall require that an adjustment
be made following a record date, a Determination Date or Expiration Date, as the
case may be, established for the purposes specified in this Section 4.06, the
Company may elect to defer (but only until five Business Days


                                       36

<PAGE>

following the filing by the Company with the Trustee of the certificate
described in Section 4.08) issuing to the Holder of any Security converted after
such record date, Determination Date or Expiration Date the shares of Common
Stock and other Capital Stock of the Company issuable upon such conversion over
and above the shares of Common Stock and other Capital Stock of the Company (or
other cash, property or securities, as applicable) issuable upon such conversion
only on the basis of the Conversion Rate prior to adjustment; and, in lieu of
any cash, property or securities the issuance of which is so deferred, the
Company shall issue or cause its transfer agents to issue due bills or other
appropriate evidence prepared by the Company of the right to receive such cash,
property or securities. If any distribution in respect of which an adjustment to
the Conversion Rate is required to be made as of the record date, Determination
Date or Expiration Date therefore is not thereafter made or paid by the Company
for any reason, the Conversion Rate shall be readjusted to the Conversion Rate
which would then be in effect if such record date had not been fixed or such
record date, Determination Date or Expiration Date had not occurred.

     (c) For purposes of this Section 4.06, "record date" shall mean, with
respect to any dividend, distribution or other transaction or event in which the
holders of Common Stock have the right to receive any cash, securities or other
property or in which the Common Stock (or other applicable security) is
exchanged or converted into any combination of cash, securities or other
property, the date fixed for determination of shareholders entitled to receive
such cash, security or other property (whether or not such date is fixed by the
Board of Directors or by statute, contract or otherwise).

     (d) If one or more event occurs requiring an adjustment be made to the
Conversion Rate for a particular period, adjustments to the Conversion Rate
shall be determined by the Company's Board of Directors to reflect the combined
impact of such Conversion Rate adjustment events, as set out in this Section
4.06, during such period.

     (e) Notwithstanding the provisions set forth in Section 4.06(a) (subject
only to the provisions of the second succeeding sentence), in no event shall the
Conversion Rate exceed 30.3674 per $1,000 principal amount of Securities,
subject to adjustment in the manner set forth in clauses (1) through (4) of
Section 4.06(a) (such limitation herein referred to as the "Conversion Rate
Cap"). The Company shall not take any action if, as a result of such action, the
adjustment to the Conversion Rate that would otherwise be made pursuant to the
provisions of clauses (6) or (7) of Section 4.06(a) would be limited by the
Conversion Rate Cap, unless such action would not result in a violation of the
National Association of Securities Dealers, Inc. ("NASD") Rule 4350 as such rule
or successor to such rule may be then in effect and interpreted by the NASD. If
such action would not result in a violation of NASD Rule 4350, then the
Conversion Rate Cap shall not apply to such action taken by the Company.

     Section 4.07 No Adjustment.

     (a) No adjustment in the Conversion Rate shall be required if Holders may
participate in the transactions set forth in Section 4.06 above (to the same
extent as if the Securities had been converted into Common Stock immediately
prior to such transactions) without converting the Securities held by such
Holders.

     (b) No adjustment in the Conversion Rate shall be required unless such
adjustment would require an increase or decrease of at least 1% in the
Conversion Rate as last adjusted; provided, however, that any adjustments which
would be required to be made but for this Section 4.07(b) shall be carried
forward and taken into account in any subsequent adjustment. All calculations
under this Article 4 shall be made to the nearest cent or to the nearest one-ten
thousandth of a share, as the case may be, with one half cent and 0.00005 of a
share, respectively, being rounded upward.


                                       37
<PAGE>

     (c) No adjustment in the Conversion Rate shall be required for issuances of
Common Stock pursuant to a Company plan for reinvestment of dividends or
interest or for a change in the par value or a change to no par value of the
Common Stock.

     (d) To the extent that the Securities become convertible into the right to
receive cash, no adjustment need be made thereafter as to the cash.

     Section 4.08 Notice of Adjustment.

     Whenever the Conversion Rate or conversion privilege is required to be
adjusted pursuant to this Indenture, the Company shall promptly mail to Holders
a notice of the adjustment and file with the Trustee an Officers' Certificate
briefly stating the facts requiring the adjustment and the manner of computing
it. Failure to mail such notice or any defect therein shall not affect the
validity of any such adjustment. Unless and until the Trustee shall receive an
Officers' Certificate setting forth an adjustment of the Conversion Rate, the
Trustee may assume without inquiry that the Conversion Rate has not been
adjusted and that the last Conversion Rate of which it has knowledge remains in
effect.

     Section 4.09 Notice of Certain Transactions.

     In the event that there is a dissolution or liquidation of the Company, the
Company shall mail to Holders and file with the Trustee a notice stating the
proposed effective date. The Company shall mail such notice at least 10 days
before such proposed effective date. Failure to mail such notice or any defect
therein shall not affect the validity of any transaction referred to in this
Section 4.09.

     Section 4.10 Effect of Recapitalization, Reclassification, Consolidation,
Merger or Sale.

     If any of following events occur (each, a "Business Combination"):

          (1) any recapitalization, reclassification or change of the Common
     Stock, other than changes resulting from a subdivision or a combination,

          (2) a consolidation, merger or combination involving the Company,

          (3) a sale, conveyance or lease to another corporation of all or
     substantially all of the property and assets of the Company, other than to
     one or more of the Company's subsidiaries, or

          (4) any statutory share exchange,

in each case as a result of which holders of Common Stock are entitled to
receive stock, other securities, other property or assets (including cash or any
combination thereof) with respect to or in exchange for Common Stock, the
Company or the successor or purchasing corporation, as the case may be, shall
execute with the Trustee a supplemental indenture (which shall comply with the
TIA as in force at the date of execution of such supplemental indenture if such
supplemental indenture is then required to so comply) providing that the Holders
of the Securities then outstanding will be entitled thereafter to convert such
Securities into the kind and amount of shares of stock, other securities or
other property or assets (including cash or any combination thereof) which they
would have owned or been entitled to receive upon such Business Combination had
such Securities been converted into Common Stock (assuming for such purpose such
conversion were settled entirely in the Company's Common Stock and without
giving effect to any adjustment to the conversion rate with respect to a
Business Combination constituting a Fundamental Change) immediately prior to
such Business Combination, except that such Holders will not receive the Make
Whole Premium if such Holder does not convert its Securities "in connection
with" the


                                       38

<PAGE>

relevant Fundamental Change. A conversion of the Securities by a Holder will be
deemed for these purposes to be "in connection with" a Fundamental Change if the
notice of such conversion is provided in compliance with Section 4.02(a) to the
Conversion Agent on or subsequent to the date 10 Trading Days prior to the date
announced by the Company as the anticipated Fundamental Change Effective Date
but before the close of business on the Business Day immediately preceding the
related Fundamental Change Purchase Date. In the event holders of Common Stock
have the opportunity to elect the form of consideration to be received in such
Business Combination, the Company shall make adequate provision whereby the
Securities shall be convertible from and after the effective date of such
Business Combination into the form of consideration elected by a majority of the
Company's stockholders in such Business Combination. Appropriate provisions will
be made, as determined in good faith by the Company's Board of Directors, to
preserve the settlement provisions in Section 4.13 following such Business
Combination to the extent feasible and to the extent the Company has not made a
Physical Settlement Election. The Company may not become a party to any such
transaction unless its terms are consistent with this Section 4.10. 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
4. If, in the case of any such Business Combination, the stock or other
securities and assets receivable thereupon by a holder of shares of Common Stock
includes shares of stock or other securities and assets of a corporation other
than the successor or purchasing corporation, as the case may be, in such
Business Combination, then such supplemental indenture shall also be executed by
such other corporation and shall contain such additional provisions to protect
the interests of the Holders of the Securities as the Board of Directors shall
reasonably consider necessary by reason of the foregoing, including to the
extent practicable the provisions providing for the repurchase rights set forth
in Article 3 hereof. Notwithstanding anything contained in this Section, and for
the avoidance of doubt, this Section shall not affect the right of a Holder to
convert its Securities into shares of Common Stock prior to the effective date
of the Business Combination.

     Section 4.11 Trustee's Disclaimer.

     (a) The Trustee shall have no duty to determine when an adjustment under
this Article 4 should be made, how it should be made or what such adjustment
should be, but may accept as conclusive evidence of that fact or the correctness
of any such adjustment, and shall be protected in relying upon, an Officers'
Certificate, including the Officers' Certificate with respect thereto which the
Company is obligated to file with the Trustee pursuant to Section 4.08. The
Trustee makes no representation as to the validity or value of any securities or
assets issued upon conversion of Securities, and the Trustee shall not be
responsible for the Company's failure to comply with any provisions of this
Article 4.

     (b) The Trustee shall not be under any responsibility to determine the
correctness of any provisions contained in any supplemental indenture executed
pursuant to Section 4.10, but may accept as conclusive evidence of the
correctness thereof, and shall be fully protected in relying upon, the Officers'
Certificate, with respect thereto which the Company is obligated to file with
the Trustee pursuant to Section 12.04.

     Section 4.12 Voluntary Increase.

     The Company from time to time may increase the Conversion Rate, to the
extent permitted by law, by any amount for any period of time if the period is
at least 20 days, and the Company provides 15 days' prior written notice to any
increase in the Conversion Rate to the Trustee and Holders. The Company may also
make such an increase to the Conversion Rate as the Board of Directors deems
advisable to avoid or diminish U.S. federal income tax to holders of shares of
Common Stock in connection with a dividend or distribution of stock (or rights
to acquire stock) or from any event treated as such for U.S. federal income tax
purposes.


                                       39

<PAGE>

     Notwithstanding the foregoing paragraph, in no event shall the Conversion
Rate exceed the Conversion Rate Cap. The Company shall not take any action if,
as a result of such action, the adjustment to the Conversion Rate that would
otherwise be made pursuant to the provisions of clauses (6) or (7) of Section
4.06(a) would be limited by the Conversion Rate Cap, unless such action would
not result in a violation of the NASD Rule 4350 as such rule or successor to
such rule may be then in effect and interpreted by the NASD. If such action
would not result in a violation of NASD Rule 4350, then the Conversion Rate Cap
shall not apply to such action taken by the Company.

     Section 4.13 Payment of Cash in Lieu of Common Stock.

     (a) Unless the Company has made a Physical Settlement Election, in lieu of
delivery of some or all of the shares of Common Stock otherwise issuable upon
notice of conversion of any Securities, Holders surrendering Securities for
conversion shall receive for each $1,000 principal amount of Securities
surrendered for conversion: (A) cash in an amount equal to the lesser of (1)
$1,000 and (2) the Conversion Value; and (B) if the Conversion Value is greater
than $1,000, a number of shares of Common Stock equal to the sum of the Daily
Share Amounts for each of the fifteen consecutive Trading Days in the Conversion
Reference Period, appropriately adjusted to reflect stock splits, stock
dividends, combinations or similar events occurring during the Conversion
Reference Period, subject to the Company's right to deliver cash in lieu of all
or a portion of such shares as set forth in Section 4.13(b); provided that in no
event shall the aggregate number of shares of Common Stock to be issued pursuant
to the foregoing clause (B), per $1,000 principal amount of Securities, exceed
the Aggregate Share Cap, without taking into account any election by the Company
to deliver cash in lieu of all or a portion of the shares of Common Stock
otherwise deliverable as set forth in Section 4.13(b). The Company will deliver
such cash and any shares of Common Stock, as applicable, together with any cash
payable for fractional shares, to such Holder in accordance with Section
4.02(a).

     (b) The Company may elect, unless the Company has made a Physical
Settlement Election, to pay cash to the Holders of Securities surrendered for
conversion in lieu of all or a portion of the Common Stock otherwise issuable
pursuant to Section 4.13(a). In such event, on any day prior to the first
Trading Day of the applicable Conversion Reference Period, the Company will
specify a percentage of the Daily Share Amount that will be settled in cash (the
"Cash Percentage") and the amount of cash that the Company will pay in respect
of each Trading Day in the applicable Conversion Reference Period will equal the
product of: (1) the Cash Percentage, (2) the Daily Share Amount for such Trading
Day and (3) the Volume Weighted Average Price of the Common Stock for such
Trading Day (provided that after the consummation of a Fundamental Change in
which the consideration is comprised entirely of cash, the amount used in this
clause (3) will be the cash price per share received by holders of the Common
Stock in such Fundamental Change). The number of shares that the Company shall
deliver in respect of each Trading Day in the applicable Conversion Reference
Period will be a percentage of the Daily Share Amount equal to 100% minus the
Cash Percentage. Upon making a determination that a percentage of the Daily
Share Amount will be settled in cash, the Company shall promptly issue a press
release and disclose such information on its website prior to the first Trading
Day of the applicable Conversion Reference Period. If the Company does not
specify a Cash Percentage by the start of the applicable Conversion Reference
Period, the Company shall settle 100% of the Daily Share Amount for each Trading
Day in the applicable Conversion Reference Period with shares of Common Stock;
provided, however, that the Company shall pay cash in lieu of fractional shares
otherwise issuable upon conversion of Securities.

     (c) For the purposes of Sections 4.13(a) and (b), in the event that any of
Conversion Value, Daily Share Amounts or Volume Weighted Average Price cannot be
determined for all portions of the Conversion Reference Period, the Company's
Board of Directors shall in good faith determine the values


                                       40

<PAGE>

necessary to calculate the Conversion Value, Daily Share Amounts and Volume
Weighted Average Price, as applicable.

     Section 4.14 Physical Settlement Election

     (a) At any time prior to the Final Maturity Date, the Company may make an
irrevocable election to provide, upon the conversion of outstanding Securities,
in lieu of providing cash and shares as provided by Section 4.13, shares of
Common Stock equal to the Conversion Rate for each $1,000 principal amount of
Securities converted (and the amount of any cash in lieu of fractional shares
pursuant to Section 4.03) (a "Physical Settlement Election"). In the event that
the Company makes a Physical Settlement Election, the Company shall promptly
issue a press release and mail to Holders and file with the Trustee a notice of
such election.

     (b) Notwithstanding anything contained in Section 4.01 to the contrary, and
subject to Section 3.01, upon making a Physical Settlement Election, any
Security or portion thereof that is an integral multiple of $1,000 principal
amount may be converted at the option of the Holder into fully paid and
nonassessable shares (calculated as to each conversion to the nearest 1/100th of
a share) of Common Stock at any time prior to the close of business on the
Business Day immediately preceding the Final Maturity Date or such earlier date
set forth in this Article 4 at the Conversion Rate in effect at such time.

     (c) Prior to making a Physical Settlement Election, the Company may
irrevocably waive the right to make a Physical Settlement Election in the future
with respect to the Securities by delivering to the Trustee a notice of such
election (a "Waiver Election"). Any Waiver Election shall irrevocably waive the
Company's ability to make a Physical Settlement Election at any time in the
future with respect to the Securities. A Waiver Election may not be made if the
Company has previously made a Physical Settlement Election.


                                       41

<PAGE>

                                    ARTICLE 5

                                    COVENANTS

     Section 5.01 Payment of Securities.

     (a) The Company shall promptly make all payments in respect of the
Securities on the dates and in the manner provided in the Securities and this
Indenture. A payment of principal or interest or Fundamental Change Purchase
Price or Additional Interest, if any, shall be considered paid on the date it is
due if the Paying Agent (other than the Company) holds by 12:00 p.m. (noon), New
York City time, on that date money, deposited by or on behalf of the Company
sufficient to make the payment. Subject to Section 4.02, accrued and unpaid
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. The Company shall, to the fullest extent permitted by law, pay
interest in immediately available funds on overdue principal amount and interest
at the annual rate borne by the Securities compounded semiannually, which
interest shall accrue from the date such overdue amount was originally 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.

     (b) Payment of the principal of and interest, if any, on the Securities
shall be made at the office or agency of the Company maintained for that purpose
(which shall initially be at the address of the Trustee set forth in Section
12.02) or at the Corporate Trust Office of the Trustee in such coin or currency
of the United States of America as at the time of payment is legal tender for
payment of public and private debts; provided, however, that at the option of
the Company payment of interest may be made by check mailed to the address of
the Person entitled thereto as such address appears in the Register; provided
further that a Holder with an aggregate principal amount in excess of $2,000,000
will be paid by wire transfer in immediately available funds at the election of
such Holder if such Holder has provided wire transfer instructions to the
Trustee at least 10 Business Days prior to the payment date. Any wire transfer
instructions received by the Trustee will remain in effect until revoked by the
Holder.

     Section 5.02 SEC and Other Reports.

     (a) The Company shall timely file all reports and other information and
documents which it is required to file with the SEC pursuant to Section 13 or
15(d) of the Exchange Act, and within 15 days after it files them with the SEC,
the Company shall file copies of all such reports, information and other
documents with the Trustee; provided that any such reports, information and
documents filed with the SEC pursuant to its Electronic Data Gathering, Analysis
and Retrieval (or EDGAR) system shall be deemed to be filed with the Trustee.
The Company also shall at all times comply with the provisions of TIA Section
314(a).

     (b) 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 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).

     Section 5.03 Compliance Certificates.

     The Company shall deliver to the Trustee, within 120 days after the end of
each fiscal year of the Company (beginning with the fiscal year ending December
31, 2007), an Officers' Certificate as to the


                                       42

<PAGE>

signer's knowledge of the Company's compliance with all conditions and covenants
on its part contained in this Indenture and stating whether or not the signer
knows of any Default or Event of Default. If such signer knows of such a Default
or Event of Default, the Officers' Certificate shall describe the Default or
Event of Default and the efforts to remedy the same. For the purposes of this
Section 5.03, compliance shall be determined without regard to any grace period
or requirement of notice provided pursuant to the terms of this Indenture.

     Section 5.04 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 5.05 Maintenance of Corporate Existence.

     Subject to Article 6, the Company will do or cause to be done all things
necessary to preserve and keep in full force and effect its corporate existence.

     Section 5.06 Rule 144A Information Requirement.

     During the period prior to the expiration of the holding period applicable
to sales thereof under Rule 144(k) under the Securities Act (or any successor
provision), the Company covenants and agrees that it shall, during any period in
which it is not subject to Section 13 or 15(d) under the Exchange Act, upon the
request of any Holder or beneficial holder of the Securities make available to
such Holder or beneficial holder of Securities or any Common Stock issued upon
conversion thereof which continue to be Restricted Securities in connection with
any sale thereof and any prospective purchaser of Securities or such Common
Stock designated by such Holder or beneficial holder, the information required
pursuant to Rule 144A(d)(4) under the Securities Act and it will take such
further action as any Holder or beneficial holder of such Securities or such
Common Stock may reasonably request, all to the extent required from time to
time to enable such Holder or beneficial holder to sell its Securities or Common
Stock without registration under the Securities Act within the limitation of the
exemption provided by Rule 144A, as such Rule may be amended from time to time.
Whether a person is a beneficial holder shall be determined by the Company.

     Section 5.07 Stay, Extension and Usury Laws.

     The Company covenants (to the extent that it may lawfully do so) that it
shall not at any time insist upon, plead, or in any manner whatsoever claim or
take the benefit or advantage of, any stay, extension or usury law or other law
which would prohibit or forgive the Company from paying all or any portion of
the principal of or accrued but unpaid interest or Additional Interest, if any,
on the Securities as contemplated herein, wherever enacted, now or at any time
hereafter in force, or which may affect the covenants or the performance of this
Indenture, and the Company (to the extent it may lawfully do so) hereby
expressly waives all benefit or advantage of any such law and covenants that it
will not, by resort to any such law, 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.

     Section 5.08 Payment of Additional Interest.

     If Additional Interest is payable by the Company pursuant to the
Registration Rights Agreement, the Company shall deliver to the Trustee an
Officers' Certificate to that effect stating (i) the amount of such Additional
Interest that is payable, (ii) the reason why such Additional Interest is
payable and (iii)


                                       43

<PAGE>

the date on which such Additional Interest is payable. Unless and until a
Responsible Officer of the Trustee receives such a certificate, the Trustee may
assume without inquiry that no such Additional Interest is payable. If the
Company has paid Additional Interest directly to the Persons entitled to such
Additional Interest, the Company shall deliver to the Trustee a certificate
setting forth the particulars of such payment.

     Section 5.09 Maintenance of Office or Agency.

     The Company will maintain an office or agency of the Trustee, Registrar and
Paying Agent where securities may be presented or surrendered for payment, where
Securities may be surrendered for registration of transfer, purchase and where
notices and demands to or upon the Company in respect of the Securities and this
Indenture may be served. The Corporate Trust Office shall initially be one such
office or agency for all of the aforesaid purposes. The Company shall give
prompt written notice to the Trustee of the location, and of any change in the
location, of any such office or agency (other than a change in the location of
the office of the Trustee). 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 address of the Trustee set forth in Section 12.02.

     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.


                                       44

<PAGE>

                                    ARTICLE 6

              CONSOLIDATION; MERGER; CONVEYANCE; TRANSFER OR LEASE

     Section 6.01 Company May Consolidate, Etc., Only on Certain Terms.

     The Company may not consolidate with or merge into any Person (unless the
Company is the surviving corporation) or convey, transfer or lease the property
and assets, substantially as an entity, of the Company to another Person, other
than to one or more of the Company's wholly-owned subsidiaries, unless:

          (1) 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 all or substantially all of the
     properties and assets of the Company, shall (i) be a corporation, limited
     liability company, partnership, trust or other business entity organized
     and existing under the laws of the United States of America or any State
     thereof or the District of Columbia and (ii) expressly assume, by an
     indenture supplemental hereto, executed and delivered to the Trustee, in
     form satisfactory to the Trustee, the obligations of the Company under the
     Securities and this Indenture and the performance or observance of every
     covenant and provision of this Indenture and the Securities required on the
     part of the Company to be performed or observed and the conversion rights
     shall be provided for in accordance with Article 4, by supplemental
     indenture satisfactory in form to the Trustee, executed and delivered to
     the Trustee, by the Person (if other than the Company) formed by such
     consolidation or into which the Company shall have been merged or by the
     Person which shall have acquired the Company's assets;

          (2) after giving effect to such transaction, no Event of Default, and
     no event which, after notice or lapse of time or both, would become an
     Event of Default, shall have occurred and be continuing; and

          (3) if the Company will not be the resulting or surviving corporation,
     the Company shall have, at or prior to the effective date of such
     consolidation, merger or transfer, delivered to the Trustee an Officers'
     Certificate and an Opinion of Counsel, each stating that such
     consolidation, merger or transfer complies with this Article 6.01 and, if a
     supplemental indenture is required in connection with such transaction,
     such supplemental indenture complies with this Article, and that all
     conditions precedent herein provided for relating to such transaction have
     been complied with.

     Section 6.02 Successor Substituted.

     Upon any consolidation of the Company with, or merger of the Company into,
any other Person or any conveyance, transfer or lease substantially as an
entity, of the properties and assets of the Company in accordance with Section
6.01, the successor Person formed by such consolidation or into which the
Company is merged or 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
Person had been named as the Company herein, and thereafter, except in the case
of a lease, and except for obligations the predecessor Person may have under a
supplemental indenture, the predecessor Person shall be relieved of all
obligations and covenants under this Indenture and the Securities.


                                       45

<PAGE>

                                    ARTICLE 7

                              DEFAULT AND REMEDIES

     Section 7.01 Events of Default.

     (a) An "Event of Default" shall occur if:

          (1) the Company shall fail to pay when due the Principal or
     Fundamental Change Purchase Price of any Security, when the same becomes
     due and payable whether at the Final Maturity Date, upon repurchase,
     acceleration or otherwise, and regardless of whether such payment is
     permitted pursuant to the subordination provisions under Article 11; or

          (2) the Company shall fail to pay an installment of cash interest or
     Additional Interest, if any, on any of the Securities, which failure
     continues for 30 days after the date when due, regardless of whether such
     payment is permitted pursuant to the subordination provisions under Article
     11; or

          (3) the Company shall fail to deliver promptly when due all cash and
     shares of Common Stock, as applicable, deliverable upon conversion of
     Securities in excess of 25% in aggregate principal amount of the Securities
     then outstanding, which failure continues for 15 days, regardless of
     whether such payment is permitted pursuant to the subordination provisions
     under Article 11; or

          (4) the Company shall fail to perform or observe (or obtain a waiver
     with respect to) any other term, covenant or agreement contained in the
     Securities or this Indenture for a period of 60 days after receipt by the
     Company of a Notice of Default specifying such failure; or

          (5) default in the payment of principal by the end of any applicable
     grace period or resulting in acceleration of other Indebtedness of the
     Company for borrowed money where the aggregate principal amount with
     respect to which the default or acceleration has occurred exceeds $15
     million and such acceleration has not been rescinded or annulled or such
     Indebtedness repaid within a period of 30 days after receipt by the Company
     of a Notice of Default, provided that if any such default is cured, waived,
     rescinded or annulled, then the Event of Default by reason thereof would
     not be deemed to have occurred; or

          (6) the Company, or any Significant Subsidiary of the Company,
     pursuant to or within the meaning of any Bankruptcy Law:

               (A) commences as a debtor a voluntary case or proceeding;

               (B) consents to the entry of an order for relief against it in an
          involuntary case or proceeding or the commencement of any case against
          it;

               (C) consents to the appointment of a Receiver of it or for all or
          substantially all of its property;

               (D) makes a general assignment for the benefit of its creditors;


                                       46

<PAGE>

               (E) files a petition in bankruptcy or answer or consent seeking
          reorganization or relief; or

               (F) consents to the filing of such a petition or the appointment
          of or taking possession by a Receiver; or

          (7) a court of competent jurisdiction enters an order or decree under
     any Bankruptcy Law that:

               (A) grants relief against the Company or any Significant
          Subsidiary of the Company in an involuntary case or proceeding or
          adjudicates the Company or any Significant Subsidiary of the Company
          insolvent or bankrupt;

               (B) appoints a Receiver of the Company or any Significant
          Subsidiary of the Company or for all or substantially all of the
          property of the Company or any Significant Subsidiary of the Company;
          or

               (C) orders the winding up or liquidation of the Company or any
          Significant Subsidiary of the Company;

     and in each case the order or decree remains unstayed and in effect for 60
consecutive days.

     The term "Bankruptcy Law" means Title 11 of the United States Code (or any
successor thereto) or any similar federal or state law for the relief of
debtors. The term "Receiver" means any receiver, trustee, assignee, liquidator,
sequestrator or similar official under any Bankruptcy Law.

     (b) Notwithstanding Section 7.01(a), no Event of Default under clauses (4)
or (5) of Section 7.01(a) shall occur until the Trustee notifies the Company in
writing, or the Holders of at least 25% in aggregate principal amount of the
Securities then outstanding notify the Company and the Trustee in writing, of
the Default (a "Notice of Default"), and the Company does not cure the Default
within the time specified in clause (4) or (5) of Section 7.01(a), as
applicable, after receipt of such notice. A notice given pursuant to this
Section 7.01 shall be given by registered or certified mail, must specify the
Default, demand that it be remedied and state that the notice is a Notice of
Default. When any Default under this Section 7.01 is cured, it ceases.

     (c) The Company will deliver to the Trustee, within sixteen Business Days
after becoming aware of the occurrence of a Default or Event of Default, written
notice thereof.

     The Trustee shall not be charged with knowledge of any Event of Default
unless written notice thereof shall have been given to a Responsible Officer
with responsibility for this Indenture at the Corporate Trust Office of the
Trustee by the Company, a Paying Agent, any Holder or any agent of any Holder or
unless a Responsible Officer with responsibility for this Indenture acquires
actual knowledge of such Event of Default in the course of performing other
duties pursuant to this Indenture.

     Section 7.02 Acceleration.

     If an Event of Default (other than an Event of Default specified in clause
(6) or (7) of Section 7.01(a)) occurs and is continuing with respect to the
Company, the Trustee may, by notice to the Company, or the Holders of at least
25% in aggregate principal amount of the Securities then outstanding may, by
notice to the Company and the Trustee, declare the principal amount and accrued
and unpaid interest, if any, and accrued and unpaid Additional Interest, if any,
through the date of declaration on all


                                       47

<PAGE>

the Securities to be immediately due and payable. Upon such a declaration, such
principal amount and such accrued and unpaid interest, if any, and such accrued
and unpaid Additional Interest, if any, shall be due and payable immediately. If
an Event of Default specified in Section 7.01(a)(6) or (7) occurs in respect of
the Company and is continuing, the principal amount and accrued but unpaid
interest, if any, and accrued and unpaid Additional Interest, if any, 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 of
Securities. The Holders of a majority in aggregate principal amount of the
Securities then outstanding by notice to the Trustee may rescind an acceleration
and its consequences if (a) all existing Events of Default, other than the
nonpayment of the principal of the Securities which have become due solely by
such declaration of acceleration, have been cured or waived; (b) to the extent
the payment of such interest is lawful, interest (calculated at the rate per
annum borne by the Securities) on overdue installments of interest and overdue
principal, which has become due otherwise than by such declaration of
acceleration, has been paid; (c) the rescission would not conflict with any
judgment or decree of a court of competent jurisdiction; and (d) all payments
due to the Trustee and any predecessor Trustee under Section 8.07 have been
made. No such rescission shall affect any subsequent Default or impair any right
consequent thereto.

     Section 7.03 Other Remedies.

     (a) If an Event of Default occurs and is continuing, the Trustee may, but
shall not be obligated to, pursue any available remedy by proceeding at law or
in equity to collect payment of the principal amount and accrued and unpaid
interest, if any, and accrued and unpaid Additional Interest, if any, on the
Securities or to enforce the performance of any provision of the Securities or
this Indenture.

     (b) The Trustee may maintain a proceeding even if it does not possess any
of the Securities or does not produce any of them 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 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 to the extent permitted by
applicable law.

     Section 7.04 Waiver of Defaults and Events of Default.

     Subject to Sections 7.07 and 10.02, the Holders of a majority in aggregate
principal amount of the Securities then outstanding by notice to the Trustee may
waive an existing Default or Event of Default and its consequences, except an
uncured Default or Event of Default in the payment of the principal of, premium,
if any, or any accrued but unpaid interest on any Security, an uncured failure
by the Company to convert Securities in excess of 25% in aggregate principal
amount of the Securities then outstanding into Common Stock and cash, as
applicable, or any Default or Event of Default in respect of any provision of
this Indenture or the Securities which, under Section 10.02, cannot be modified
or amended without the consent of the Holder of each Security affected. When a
Default or Event of Default is waived, it is cured and ceases to exist.

     Section 7.05 Control by Majority.

     The Holders of a majority in aggregate principal amount of the Securities
then outstanding may direct the time method and place of conducting any
proceeding for any remedy available to the Trustee or exercising any trust or
power conferred on it. However, the Trustee may refuse to follow any direction
that conflicts with law or this Indenture, that the Trustee determines may be
unduly prejudicial to the rights of another Holder or the Trustee, or that may
involve the Trustee in personal liability unless the Trustee is offered security
or indemnity satisfactory to it; provided, however, that the Trustee may take
any other action deemed proper by the Trustee which is not inconsistent with
such direction.


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<PAGE>

     Section 7.06 Limitations on Suits.

     (a) A Holder may not pursue any remedy with respect to this Indenture or
the Securities (except actions for payment of overdue principal, premium, if
any, or interest or for the conversion of the Securities pursuant to Article 4)
unless:

          (1) the Holder gives to the Trustee written notice of a continuing
     Event of Default;

          (2) the Holders of at least 25% in aggregate principal amount of the
     then outstanding Securities make a written request to the Trustee to pursue
     the remedy;

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

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

          (5) no direction inconsistent with such written request has been given
     to the Trustee during such 60-day period by the Holders of a majority in
     aggregate principal amount of the Securities then outstanding.

     (b) No Holder of a Security shall have any right under any provision of
this Indenture or the Securities to affect, disturb, or prejudice the rights of
another Holder of a Security or to obtain a preference or priority over another
Holder of a Security.

     Section 7.07 Rights of Holders to Receive Payment and to Convert.

     Notwithstanding any other provision of this Indenture but subject to the
provisions of Article 11 hereof, the right of any Holder of a Security to
receive payment of the principal amount, interest, Fundamental Change Purchase
Price, if any, or Additional Interest, if any, in respect of the Securities held
by such Holder, on or after the respective due dates expressed in the Securities
and this Indenture (whether upon repurchase or otherwise), and to convert such
Security in accordance with Article 4, and to bring suit for the enforcement of
any such payment on or after such respective due dates or for the right to
convert in accordance with Article 4, is absolute and unconditional and shall
not be impaired or affected without the consent of the Holder.

     Section 7.08 Collection Suit by Trustee.

     If an Event of Default described in clause (1) or (2) of Section 7.01(a)
occurs and is continuing, the Trustee may recover judgment in its own name and
as trustee of an express trust against the Company or another obligor on the
Securities for the whole amount owing with respect to the Securities and such
further amount as shall be sufficient to cover the costs and expenses of
collection, including the reasonable compensation, expenses, disbursements and
advances of the Trustee, its agents and counsel.

     Section 7.09 Trustee May File Proofs of Claim.

     The Trustee may file such proofs of claim and 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 the Holders allowed in
any judicial proceedings relative to the Company (or any other obligor on the
Securities), its creditors or its property and shall be entitled and empowered
to collect and receive any money or other property


                                       49

<PAGE>

payable or deliverable on any such claims and to distribute the same, and any
Receiver 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 to the Holders, to pay to the
Trustee any amount due to 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 8.07, and to the extent that such payment
of the reasonable compensation, expenses, disbursements and advances in any such
proceedings shall be denied for any reason, payment of the same shall be secured
by a lien on, and shall be paid out of, any and all distributions, dividends,
money, securities and other property which the Holders may be entitled to
receive in such proceedings, whether in liquidation or under any plan of
reorganization or arrangement or otherwise. Nothing herein contained shall be
deemed to authorize the Trustee to authorize or consent to, or, on behalf of any
Holder, to authorize, accept or adopt 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 claim of any
Holder in any such proceeding.

     Section 7.10 Priorities.

     (a) If the Trustee collects any money pursuant to this Article 7, it shall
pay out the money in the following order:

          (1) First, to the Trustee for amounts due under Section 8.07;

          (2) Second, to the Holders of Senior Indebtedness to the extent
     required by Article 11;

          (3) Third, to Holders for amounts due and unpaid on the Securities for
     the principal amount, interest, and Additional Interest, as applicable,
     ratably, without preference or priority of any kind, according to such
     respective amounts due and payable on the Holders' Securities;

          (4) Fourth, to such other Person or Persons, if any, to the extent
     entitled thereto; and

          (5) Fifth, the balance, if any, to the Company.

     (b) The Trustee may fix a record date and payment date for any payment to
Holders pursuant to this Section 7.10.

     Section 7.11 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
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 to the
merits and good faith of the claims or defenses made by the party litigant. This
Section 7.11 does not apply to a suit made by the Trustee, a suit by a Holder
pursuant to Section 7.07, or a suit by Holders of more than 10% in aggregate
principal amount of the Securities then outstanding. This Section 7.11 shall be
in lieu of Section 315(e) of the TIA and such Section 315(e) is hereby expressly
excluded from this Indenture, as permitted by the TIA.


                                       50

<PAGE>

                                    ARTICLE 8

                                     TRUSTEE

     Section 8.01 Obligations of Trustee.

     (a) If an Event of Default of which a Responsible Officer of the Trustee
shall have actual knowledge has occurred and is continuing, the Trustee shall
exercise such of 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 person would
exercise or use under the circumstances in the conduct of his or her own
affairs.

     (b) Except during the continuance of an Event of Default of which a
Responsible Officer of the Trustee shall have actual knowledge:

          (1) the Trustee need perform only those duties as 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. The
     Trustee, however, shall examine any certificates and opinions which by any
     provision hereof are specifically required to be delivered to the Trustee
     to determine whether or not they conform to the requirements of this
     Indenture, but need not confirm or investigate the accuracy of mathematical
     calculations or other facts stated therein.

          This Section 8.01(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 gross
negligent action, its own gross negligent failure to act, or its own willful
misconduct, except that:

          (1) this paragraph does not limit the effect of Section 8.01(b);

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

          (3) the Trustee shall not be liable in its individual capacity with
     respect to any action it takes or omits to take in good faith in accordance
     with this Indenture or a direction received by it pursuant to Section 7.05.

          This Section 8.01(c) shall be in lieu of Sections 315(d)(1), 315(d)(2)
     and 315(d)(3) of the TIA and such Sections are hereby expressly excluded
     from this Indenture as permitted by the TIA.

     (d) No provision of this Indenture shall require the Trustee to expend or
risk its own funds or otherwise incur any financial liability in the performance
of any of its duties hereunder or in the exercise of any of its rights or powers
unless the Trustee shall have received adequate security or indemnity in its
opinion against potential costs and liabilities incurred by it relating thereto.


                                       51

<PAGE>

     (e) Every provision of this Indenture that in any way relates to the
Trustee is subject to subsections (a), (b), (c) and (d) of this Section 8.01.

     (f) The Trustee shall not be liable for interest on any money received by
it except as the Trustee may agree in writing with the Company. Money held in
trust by the Trustee need not be segregated from other funds except to the
extent required by law.

     Section 8.02 Rights of Trustee.

     (a) Subject to Section 8.01:

          (1) The Trustee may rely conclusively and shall be protected in acting
     or refraining from acting upon on any document 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.

          (2) Before the Trustee acts or refrains from acting, it may require an
     Officers' Certificate or an Opinion of Counsel, which shall conform to
     Section 12.04(b). The Trustee shall not be liable for any action it takes
     or omits to take in good faith in reliance on such Officers' Certificate or
     Opinion of Counsel.

          (3) The Trustee may execute any of the trusts or powers hereunder or
     perform any duties hereunder either directly or by or through agents,
     attorneys or custodians, and the Trustee shall not be responsible for any
     misconduct or negligence on the part of any such agent, attorney or
     custodian appointed by the Trustee with due care.

          (4) The Trustee shall not be personally 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.

          (5) The Trustee may consult with counsel of its selection, and the
     advice or opinion of such counsel as to matters of law shall be full and
     complete authorization and protection in respect of any such action taken,
     omitted or suffered by it hereunder in good faith and in accordance with
     the advice or opinion of such counsel.

          (6) The Trustee shall be under no obligation to exercise any of the
     rights or powers vested in it by this Indenture or to institute, conduct or
     defend any litigation hereunder or in relation hereto at the request or
     direction of any of the Holders pursuant to this Indenture, unless such
     Holders shall have offered to the Trustee security or indemnity
     satisfactory to the Trustee against the costs, expenses and liabilities
     which might be incurred by it in compliance with such request or direction.

          (7) 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 such 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, 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. The reasonable expense of every
     such examination shall be paid by the Company or, if paid by the Trustee,
     shall be repaid by the Company upon demand from the Company's own funds.


                                       52

<PAGE>

          (8) The Trustee shall not be deemed to have notice or knowledge of any
     Default, Event of Default, or Fundamental Change unless a Responsible
     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, and such notice references the
     Securities and this Indenture. In the absence of receipt of such notice or
     actual knowledge, the Trustee may conclusively assume that there is no
     Default, Event of Default, or Fundamental Change.

          (9) 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, including, without limitation as Paying Agent,
     Registrar and Conversion Agent, and to each agent, custodian and other
     Person employed to act hereunder.

          (10) The right of the Trustee to perform any discretionary act
     enumerated in this Indenture shall not be construed as a duty, and the
     Trustee shall not be answerable for other than its own gross negligence or
     willful misconduct in the performance of such act.

     Section 8.03 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 an Affiliate of
the Company with the same rights it would have if it were not Trustee. Any Agent
may do the same with like rights. However, the Trustee is subject to Sections
8.10 and 8.11.

     Section 8.04 Trustee's Disclaimer.

     The Trustee makes no representation as to the validity or adequacy of this
Indenture or the Securities and the Trustee assumes no responsibility for their
correctness. 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
Securities other than its certificate of authentication.

     Section 8.05 Notice of Default or Events of Default.

     If a Default or an Event of Default occurs and is continuing and if it is
known to the Trustee, the Trustee shall mail to each Holder of a Security notice
of all uncured Defaults or Events of Default known to it within 90 days after it
occurs or, if later, within 15 days after it becomes known to the Trustee.
However, the Trustee may withhold the notice if and for so long as a committee
of its Responsible Officers in good faith determines that withholding notice is
in the interests of Holders of Securities, except in the case of a Default or an
Event of Default in payment of the principal of, or premium, if any, or interest
on any Security when due or in the payment of any purchase obligation, or the
Company's failure to convert Securities when obligated to convert them. This
Section 8.05 is in lieu of section 315(b) of the TIA and such provision is
expressly excluded from this Indenture as permitted by the TIA.

     Section 8.06 Reports by Trustee to Holders.

     (a) If a report is required by TIA Section 313, within 60 days after each
May 15, beginning with the May 15 following the date of this Indenture, the
Trustee shall mail to each Holder of Securities a brief report dated as of such
May 15 that complies with TIA Section 313(a). If required by TIA Section 313,
the Trustee also shall comply with TIA Sections 313(b)(2) and (c).


                                       53
<PAGE>

     (b) A copy of each report at the time of its mailing to Holders of
Securities shall be mailed to the Company and, to the extent required by the
TIA, filed with the SEC, and each stock exchange, if any, on which the
Securities are listed. The Company shall notify the Trustee whenever the
Securities become listed on any stock exchange or listed or admitted to trading
on any quotation system and any changes in the stock exchanges or quotation
systems on which the Securities are listed or admitted to trading and of any
delisting thereof.

     Section 8.07 Compensation and Indemnity.

     (a) The Company shall pay to the Trustee from time to time such
compensation (as agreed to from time to time by the Company and the Trustee in
writing) for its services (which compensation shall not be limited by any
provision of law in regard to the compensation of a trustee of an express
trust). The Company shall reimburse the Trustee upon request for all reasonable
disbursements, expenses and advances incurred or made by it. Such expenses may
include the reasonable compensation, disbursements and expenses of the Trustee's
agents and counsel.

     (b) The Company shall indemnify the Trustee or any predecessor Trustee
(which for purposes of this Section 8.07 shall include its officers, directors,
employees and agents) for, and hold it harmless against, any and all loss,
liability or expense including taxes (other than franchise taxes and taxes based
upon, measured by or determined by the income of the Trustee), incurred by it in
connection with the acceptance or administration of its duties under this
Indenture or any action or failure to act as authorized or within the discretion
or rights or powers conferred upon the Trustee hereunder including the
reasonable costs and expenses of the Trustee and its counsel in defending
(including reasonable legal fees and expenses) itself against any claim or
liability in connection with the exercise or performance of any of its powers or
duties hereunder. The Trustee shall notify the Company promptly of any claim
asserted against the Trustee for which it may seek indemnity. The Company need
not pay for any settlement effected without its prior written consent, which
shall not be unreasonably withheld. Anything in this Indenture to the contrary
notwithstanding, in no event shall the Trustee be liable for special, indirect
or consequential loss or damage of any kind whatsoever (including but not
limited to lost profits), even if the Trustee has been advised of the likelihood
of such loss or damage and regardless of the form of action.

     (c) The Company need not reimburse the Trustee for any expense or indemnify
it against any loss or liability incurred by it resulting from its gross
negligence, willful misconduct or bad faith.

     (d) The Trustee shall have a senior claim to which the Securities are
hereby made subordinate on all money or property held or collected by the
Trustee. The obligations of the Company under this Section 8.07 shall survive
the satisfaction and discharge of this Indenture or the resignation or removal
of the Trustee.

     (e) When the Trustee incurs expenses or renders services after an Event of
Default specified in clause (6) or (7) of Section 7.01(a) occurs, the expenses
and the compensation for the services are intended to constitute expenses of
administration under any Bankruptcy Law. The provisions of this Section shall
survive the termination of this Indenture or the resignation or removal of the
Trustee.


                                       54

<PAGE>

     Section 8.08 Replacement of Trustee.

     (a) The Trustee may resign by so notifying the Company. The Holders of a
majority in aggregate principal amount of the Securities then outstanding may
remove the Trustee by so notifying the Trustee and the Company and may, with the
Company's written consent, appoint a successor Trustee. The Company may remove
the Trustee at any time, so long as no Default or Event of Default has occurred
and is continuing, and appoint a Successor Trustee in accordance with this
Section 8.08.

     (b) 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 a successor
Trustee. If the Company fails to promptly appoint a successor Trustee, the
Trustee shall have the right to choose a qualified Trustee as successor, and the
Company shall appoint such successor as Trustee. The resignation or removal of a
Trustee shall not be effective until a successor Trustee shall have delivered
the written acceptance of its appointment as described below.

     (c) 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 10% in principal amount of the Securities then outstanding may
petition any court of competent jurisdiction for the appointment of a successor
Trustee at the expense of the Company.

     (d) If the Trustee fails to comply with Section 8.10, any Holder may
petition any court of competent jurisdiction for the removal of the Trustee and
the appointment of a successor Trustee.

     (e) A successor Trustee shall deliver a written acceptance of its
appointment to the retiring Trustee and to the Company. Immediately after that,
the retiring Trustee shall transfer all property held by it as Trustee to the
successor Trustee and be released from its obligations (exclusive of any
liabilities that the retiring Trustee may have incurred while acting as Trustee)
hereunder, the resignation or removal of the retiring Trustee shall become
effective, and the successor Trustee shall have all the rights, powers and
duties of the Trustee under this Indenture. A successor Trustee shall mail
notice of its succession to each Holder.

     (f) A retiring Trustee shall not be liable for the acts or omissions of any
successor Trustee after its succession.

     (g) Notwithstanding replacement of the Trustee pursuant to this Section
8.08, the Company's obligations under Section 8.07 shall continue for the
benefit of the retiring Trustee.

     Section 8.09 Successor Trustee by Merger, Etc.

     If the Trustee consolidates with, merges or converts into, or transfers all
or substantially all of its corporate trust business (including the
administration of this Indenture) to, another corporation, the resulting,
surviving or transferee corporation, without any further act, shall be the
successor Trustee; provided such transferee corporation shall qualify and be
eligible under Section 8.10. Such successor Trustee shall promptly mail notice
of its succession to the Company and each Holder.

     Section 8.10 Eligibility; Disqualification.

     The Trustee shall always satisfy the requirements of paragraphs (1), (2)
and (5) of TIA Section 310(a). The Trustee (or its parent 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 condition. If at any time the Trustee
shall cease to satisfy any such requirements, it shall resign immediately in the
manner and with the effect


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<PAGE>

specified in this Article 8. The Trustee shall be subject to the provisions of
TIA Section 310(b). Nothing herein shall prevent the Trustee from filing with
the SEC the application referred to in the penultimate paragraph of TIA Section
310(b).

     Section 8.11 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.


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                                    ARTICLE 9

                     SATISFACTION AND DISCHARGE OF INDENTURE

     Section 9.01 Satisfaction and Discharge of Indenture.

     (a) This Indenture shall cease to be of further force and effect (except as
to any surviving rights of conversion, registration of transfer or exchange of
Securities herein expressly provided for and except as further provided below),
and the Trustee, on demand of and at the expense of the Company, shall execute
proper instruments acknowledging satisfaction and discharge of this Indenture,
when either:

               (A) all Securities theretofore authenticated and delivered (other
          than (i) Securities which have been destroyed, lost or stolen and
          which have been replaced or paid as provided in Section 2.07 and (ii)
          Securities for whose payment money has theretofore been deposited in
          trust and thereafter repaid to the Company as provided in Section
          9.03) have been delivered to the Trustee for cancellation; or

               (B) all such Securities not theretofore delivered to the Trustee
          for cancellation have become due and payable, provided, that

          (1) the Company has deposited with the Trustee or a Paying Agent
     (other than the Company or any of its Affiliates) immediately available
     funds in trust for the purpose of and in an amount sufficient to pay and
     discharge all indebtedness related to such Securities not theretofore
     delivered to the Trustee for cancellation, for principal and interest to
     the date of such deposit;

          (2) the Company has paid or caused to be paid all other sums payable
     hereunder by the Company; and

          (3) the Company has delivered to the Trustee an Officers' Certificate
     and an Opinion of Counsel, each stating that all conditions precedent
     herein relating to the satisfaction and discharge of this Indenture have
     been complied with.

     (b) Notwithstanding the satisfaction and discharge of this Indenture, the
obligations of the Company with respect to the conversion privilege and the
Conversion Rate of the Securities pursuant to Article 4, the obligations of the
Company to the Trustee under Section 8.07 and, if money shall have been
deposited with the Trustee pursuant to clause (2) of Section 9.01(a), the
provisions of Sections 2.03, 2.04, 2.05, 2.06, 2.07, 2.12, 5.01 and 12.05,
Article 4, and this Article 9, shall survive until the Securities have been paid
in full.

     Section 9.02 Application of Trust Money.

     Subject to the provisions of Section 9.03, the Trustee or a Paying Agent
shall hold in trust, for the benefit of the Holders, all money deposited with it
pursuant to Section 9.01 and shall apply the deposited money in accordance with
this Indenture and the Securities to the payment of the principal of and
interest on the Securities.

     Section 9.03 Repayment to Company.

     (a) The Trustee and each Paying Agent shall promptly pay to the Company
upon request any excess money (1) deposited with them pursuant to Section 9.01
and (2) held by them at any time.


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<PAGE>

     (b) The Trustee and each Paying Agent shall, subject to applicable
abandonment property laws, pay to the Company upon request any money held by
them for the payment of principal or interest that remains unclaimed for two
years after a right to such money has matured; provided, however, that the
Trustee or such Paying Agent, before being required to make any such payment,
may at the expense of the Company cause to be mailed to each Holder entitled to
such money notice that such money remains unclaimed and that after a date
specified therein, which shall be at least 30 days from the date of such
mailing, any unclaimed balance of such money then remaining will be repaid to
the Company. After payment to the Company, Holders entitled to money must look
to the Company for payment as general creditors unless an applicable abandoned
property law designates another person.

     Section 9.04 Reinstatement.

     If the Trustee or any Paying Agent is unable to apply any money in
accordance with Section 9.02 by reason of any legal proceeding or by reason of
any order or judgment of any court or governmental authority enjoining,
restraining or otherwise prohibiting such application, then the Company's
obligations under this Indenture and the Securities shall be revived and
reinstated as though no deposit had occurred pursuant to Section 9.01 until such
time as the Trustee or such Paying Agent is permitted to apply all such money in
accordance with Section 9.02; provided, however, that if the Company has made
any payment of the principal of or interest on any Securities because of the
reinstatement of its obligations, the Company shall be subrogated to the rights
of the Holders of such Securities to receive any such payment from the money
held by the Trustee or such Paying Agent.


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                                   ARTICLE 10

                       AMENDMENTS; SUPPLEMENTS AND WAIVERS

     Section 10.01 Without Consent of Holders.

     (a) The Company and the Trustee may amend or supplement this Indenture or
the Securities without notice to or consent of any Holder of a Security for the
purpose of:

          (1) evidencing a successor to the Company and the assumption by that
     successor of the Company's obligations under this Indenture and the
     Securities;

          (2) adding to the Company's covenants for the benefit of the Holders
     or surrendering any right or power conferred upon the Company;

          (3) securing the Company's obligations in respect of the Securities;

          (4) evidencing and providing for the acceptance of the appointment of
     a successor trustee in accordance with Article 8;

          (5) complying with the requirements of the SEC in order to effect or
     maintain the qualification of this Indenture under the TIA, as contemplated
     by this Indenture or otherwise;

          (6) curing any ambiguity, omission, inconsistency or correcting or
     supplementing any defective provision contained in this Indenture; or

          (7) modifying any other provisions of this Indenture in any manner
     that will not adversely affect the rights of the Holders in any material
     respect.

     Section 10.02 With Consent of Holders.

     (a) The Company and the Trustee may amend or supplement this Indenture or
the Securities with the written consent of the Holders of at least a majority in
aggregate principal amount of the Securities then outstanding. However, subject
to Section 10.04, without the written consent of each Holder affected, an
amendment, supplement or waiver may not:

          (1) alter the manner of calculation or decrease the rate of accrual of
     interest on any Security or change the time of payment of any installment
     of interest on, or any Additional Interest with respect to, any Security;

          (2) make any of the Securities payable in money or securities other
     than that stated in the Securities;

          (3) change the stated maturity of any Security;

          (4) reduce the principal amount or Fundamental Change Purchase Price
     (including any Make Whole Premium payable) (as applicable) with respect to
     any of the Securities, or any Additional Interest, or purchase pursuant to
     Article 3, with respect to any Security;


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<PAGE>

          (5) make any change that adversely affects the conversion rights of a
     Holder in any material respect other than as provided herein (including,
     without limitation, the Company's right to make a Physical Settlement
     Election);

          (6) make any change that adversely affects the rights of Holders to
     require the Company to purchase Securities at the option of Holders;

          (7) impair the right to institute suit for the enforcement of any
     payment on or with respect to any Security or with respect to the
     conversion of any Security;

          (8) change the currency of payment of principal of, or interest on,
     the Securities;

          (9) except as otherwise permitted or contemplated by Section 4.10,
     adversely affect the conversion rights of the Securities; or

          (10) reduce the percentage in aggregate principal amount of Securities
     outstanding necessary to modify or amend this Indenture or to waive any
     past Default or otherwise change the provisions in this Indenture that
     relate to modifying or amending this Indenture.

     (b) Without limiting the provisions of Section 10.02(a) hereof, the Holders
of a majority in principal amount of the Securities then outstanding may, on
behalf of all the Holders of all Securities, (i) waive compliance by the Company
with the restrictive provisions of this Indenture, and (ii) waive any past
Default or Event of Default under this Indenture and its consequences, except an
uncured failure to pay when due the principal amount, accrued and unpaid
interest, accrued and unpaid Additional Interest or Fundamental Change Purchase
Price, or in the obligation to deliver Common Stock or cash, as applicable, or
in respect of any provision which under this Indenture cannot be modified or
amended without the consent of the Holder of each outstanding Security affected.

     (c) After an amendment, supplement or waiver under this Section 10.02
becomes effective, the Company shall promptly mail to the Holders affected
thereby a notice briefly describing the amendment, supplement or waiver. Any
failure of the Company to mail such notice, or any defect therein, shall not,
however, in any way impair or affect the validity of any such amendment,
supplement or waiver.

     Section 10.03 Compliance with Trust Indenture Act.

     Every amendment to or supplement of this Indenture or the Securities shall
comply with the TIA as in effect at the date of such amendment or supplement.

     Section 10.04 Revocation and Effect of Consents.

     (a) Until an amendment, supplement or waiver becomes effective, a consent
to it by a Holder is a continuing consent by the Holder and every subsequent
Holder of a Security or portion of a Security that evidences the same debt as
the consenting Holder's Security, even if notation of the consent is not made on
any Security. However, any such Holder or subsequent Holder may revoke the
consent as to its Security or portion of a Security if the Trustee receives the
notice of revocation before the date the amendment, supplement or waiver becomes
effective.

     (b) After an amendment, supplement or waiver becomes effective, it shall
bind every Holder of a Security.


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<PAGE>

     Section 10.05 Notation on or Exchange of Securities.

     If an amendment, supplement or waiver changes the terms of a Security, the
Trustee may require the Holder of the Security to deliver it to the Trustee. The
Trustee may place an appropriate notation on the Security about the changed
terms and return it to the Holder. Alternatively, if the Company or the Trustee
so determines, the Company in exchange for the Security shall issue and the
Trustee shall authenticate a new Security that reflects the changed terms.

     Section 10.06 Trustee to Sign Amendments, Etc.

     The Trustee shall sign any amendment or supplemental indenture authorized
pursuant to this Article 10 if the amendment or supplemental indenture does not
adversely affect the rights, duties, liabilities or immunities of the Trustee.
If it does, the Trustee may, in its sole discretion, but need not sign it. In
signing or refusing to sign such amendment or supplemental indenture, the
Trustee shall be entitled to receive and, subject to Section 8.01, shall be
fully protected in relying upon, an Opinion of Counsel stating that such
amendment or supplemental indenture is authorized or permitted by this
Indenture. The Company may not sign an amendment or supplemental indenture until
the Board of Directors approves it.

     Section 10.07 Effect of Supplemental Indentures.

     Upon the execution of any supplemental indenture under this Article 10,
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.


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<PAGE>

                                   ARTICLE 11

                                  SUBORDINATION

     Section 11.01 Agreement to Subordinate.

     The Company covenants and agrees, and each Holder by accepting a Security
likewise covenants and agrees, that all Securities shall be issued subject to
the provisions of this Article 11; and each Person holding any Security, whether
upon original issue or upon transfer, assignment or exchange thereof, accepts
and agrees to be bound by such provisions.

     The payment of the principal of, premium, if any, interest, and Additional
Interest, if any, on all Securities (including, but not limited to, the
Fundamental Change Purchase Price with respect to the Securities subject to
repurchase in accordance with Article 3 as provided in this Indenture) issued
hereunder shall, to the extent and in the manner hereinafter set forth, be
subordinated and subject in right of payment to the prior payment of all Senior
Indebtedness, whether outstanding at the date of this Indenture or thereafter
incurred, in full in cash or payment satisfactory to the holders of Senior
Indebtedness.

     No provision of this Article 11 shall prevent the occurrence of any Default
or Event of Default hereunder.

     Section 11.02 Payment to Holders.

     No payment shall be made with respect to the principal of, or premium, if
any, interest and Additional Interest, if any, on the Securities (including, but
not limited to, the Fundamental Change Purchase Price with respect to the
Securities subject to repurchase in accordance with Article 3 as provided in
this Indenture), and no repurchase or retirement of the Securities shall occur
and no deposit shall be made pursuant to Article 9 at a time when such deposited
amounts would not otherwise be permitted under this Article 11, other than
through the delivery of Common Stock (but not the cash portion of the Company's
conversion obligation) in respect of the conversion of Securities if:

          (a) a default in the payment of principal, premium, interest, rent or
     other obligations due on any Senior Indebtedness occurs and is continuing
     (or, in the case of Senior Indebtedness for which there is a period of
     grace, in the event of such a default that continues beyond the period of
     grace, if any, specified in the instrument or lease evidencing such Senior
     Indebtedness), unless and until such default shall have been cured or
     waived by the appropriate holders of the Senior Indebtedness or shall have
     ceased to exist; or

          (b) a default, other than a payment default, on any Designated Senior
     Indebtedness occurs and is continuing that then permits holders of such
     Designated Senior Indebtedness to accelerate the maturity of all or any
     portion of such Designated Senior Indebtedness (or would permit such
     holders to so accelerate with the giving of notice or the passage of time
     or both) and the Trustee receives a notice of the default (a "Payment
     Blockage Notice") from a Representative or holder of such Designated Senior
     Indebtedness or the Company.

     Subject to the provisions of Section 11.05, if the Trustee receives any
Payment Blockage Notice pursuant to clause (b) above, no subsequent Payment
Blockage Notice shall be effective for purposes of this Section unless and until
at least 365 days shall have elapsed since the initial effectiveness of the
immediately prior Payment Blockage Notice. No nonpayment default that existed or
was continuing on the date of delivery of any Payment Blockage Notice to the
Trustee (unless such default was waived,


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<PAGE>

cured or otherwise ceased to exist and thereafter subsequently reoccurred) shall
be, or be made, the basis for a subsequent Payment Blockage Notice, whether or
not within a period of 365 consecutive days.

     Unless this Article 11 otherwise prohibits payments on or distributions in
respect of the Securities at the time of such payments or distributions, the
Company may and shall resume such payments on and distributions:

          (A) in the case of a default referred to in clause (a) above, the date
     upon which the default is cured or waived by the requisite holders of
     Senior Indebtedness or otherwise ceases to exist, or

          (B) in the case of a default referred to in clause (b) above, the
     earliest to occur of (i) the date on which such default is cured or waived
     or otherwise ceases to exist or such Designated Senior Indebtedness is
     discharged or paid in full, (ii) 179 days pass after the date on which the
     applicable Payment Blockage Notice is received, and (iii) the date such
     payment blockage period shall have been terminated by written notice to the
     Company or the Trustee from the Person initiating such payment blockage
     period provided that, if the maturity of such Designated Senior
     Indebtedness has been accelerated no payment may be made on the Securities
     until such acceleration is cured or waived or otherwise ceases to exist or
     such Designated Senior Indebtedness is discharged or paid in full.

     Upon any payment by the Company, or distribution of assets of the Company
of any kind or character, whether in cash, property or securities, to creditors
upon any dissolution or winding-up or liquidation or reorganization of the
Company (whether voluntary or involuntary) or in bankruptcy, insolvency,
receivership or similar proceedings, all amounts due or to become due upon all
Senior Indebtedness shall first be paid in full in cash, or other payment
satisfactory to the holders of Senior Indebtedness, before any payment is made
on account of the principal of, premium, if any, interest or Additional
Interest, if any, on the Securities (including, but not limited to, the
Fundamental Change Purchase Price with respect to the Securities subject to
repurchase in accordance with Article 3 as provided in this Indenture); and upon
any such dissolution or winding-up or liquidation or reorganization of the
Company or bankruptcy, insolvency, receivership or other proceeding, any payment
by the Company, or distribution of assets of the Company of any kind or
character, whether in cash, property or securities, to which the Holders or the
Trustee would be entitled, except for the provision of this Article 11, shall
(except as aforesaid) be paid by the Company or by any receiver, trustee in
bankruptcy, liquidating trustee, agent or other Person making such payment or
distribution, or by the Holders or by the Trustee under this Indenture if
received by them or it, directly to the holders of Senior Indebtedness (pro rata
to such holders on the basis of the respective amounts of Senior Indebtedness
held by such holders, or as otherwise required by law or a court order) or their
Representative or Representatives, as their respective interests may appear, to
the extent necessary to pay all Senior Indebtedness in full in cash, or other
payment satisfactory to the holders of Senior Indebtedness, after giving effect
to any concurrent payment or distribution to or for the holders of Senior
Indebtedness, before any payment or distribution is made to the Holders or to
the Trustee.

     For purposes of this Article 11, the words, "cash, property or securities"
shall not be deemed to include shares of stock of the Company as reorganized or
readjusted, or securities of the Company or any other corporation provided for
by a plan of reorganization or readjustment, the payment of which is
subordinated at least to the extent provided in this Article 11 with respect to
the Securities to the payment of all Senior Indebtedness which may at the time
be outstanding; provided that (i) the Senior Indebtedness is assumed by the new
corporation, if any, resulting from any reorganization or readjustment, and (ii)
the rights of the holders of Senior Indebtedness (other than leases which are
not assumed by the Company or the new corporation, as the case may be) are not,
without the consent of such holders, altered by such


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<PAGE>

reorganization or readjustment. The consolidation of the Company with, or the
merger of the Company into, another corporation or the liquidation or
dissolution of the Company following the conveyance, transfer, sale, lease or
other disposition of its property as an entirety, or substantially as an
entirety, to another corporation upon the terms and conditions provided for in
Article 6 shall not be deemed a dissolution, winding-up, liquidation or
reorganization for the purposes of this Section 11.02 if such other corporation
shall, as a part of such consolidation, merger, conveyance, transfer, sale,
lease or other disposition, comply with the conditions stated in Article 6.

     In the event of the acceleration of the Securities because of an Event of
Default, no payment or distribution shall be made to the Trustee or any Holders
in respect of the principal of, premium, if any, interest or Additional
Interest, if any, on the Securities by the Company (including, but not limited
to, the Fundamental Change Purchase Price with respect to the Securities subject
to repurchase in accordance with Article 3 as provided in this Indenture),
except payments and distributions made by the Trustee as permitted by Section
11.05, until all Senior Indebtedness has been paid in full in cash or other
payment satisfactory to the holders of Senior Indebtedness or such acceleration
is rescinded in accordance with the terms of this Indenture. If payment of the
Securities is accelerated because of an Event of Default, the Company shall
promptly notify holders of Designated Senior Indebtedness of such acceleration.

     In the event that, notwithstanding the foregoing provisions, any payment or
distribution of assets of the Company of any kind or character, whether in cash,
property or securities (including, without limitation, by way of setoff or
otherwise), prohibited by the provisions of this Article 11, shall be received
by the Trustee or any of the Holders before all Senior Indebtedness is paid in
full, in cash or other payment satisfactory to the holders of Senior
Indebtedness, or provision is made for such payment thereof in accordance with
its terms in cash or other payment satisfactory to the holders of Senior
Indebtedness, such payment or distribution shall be held in trust for the
benefit of and shall be paid over or delivered to the holders of Senior
Indebtedness or their Representative or Representatives, as their respective
interests may appear, as calculated by the Company.

     Nothing in this Section 11.02 shall apply to claims of, or payments to, the
Trustee under or pursuant to Section 8.07. This Section 11.02 shall be subject
to the further provisions of Section 11.05.

     Section 11.03 Subrogation of Securities.

     After the payment in full, in cash or other payment satisfactory to the
holders of Senior Indebtedness, of all Senior Indebtedness (and all commitments
with respect to such Senior Indebtedness have terminated or expired), the rights
of the Holders shall be subrogated to the extent of the payments or
distributions made to the holders of such Senior Indebtedness pursuant to the
provisions of this Article 11 (equally and ratably with the holders of all
indebtedness of the Company which by its express terms is subordinated to other
indebtedness of the Company to substantially the same extent as the Securities
are subordinated and is entitled to like rights of subrogation) to the rights of
the holders of Senior Indebtedness to receive payments or distributions of cash,
property or securities of the Company applicable to the Senior Indebtedness
until the principal, premium, if any, interest or Additional Interest, if any,
on the Securities shall be paid in full in cash or other payment satisfactory to
the holders of Senior Indebtedness; and, for the purposes of such subrogation,
no payments or distributions to the holders of the Senior Indebtedness of any
cash, property or securities to which the Holders or the Trustee would be
entitled except for the provisions of this Article 11, and no payment over
pursuant to the provisions of this Article 11, to or for the benefit of the
holders of Senior Indebtedness by Holders or the Trustee, shall, as between the
Company, its creditors other than holders of Senior Indebtedness, and the
Holders, be deemed to be a payment by the Company to or on account of the Senior
Indebtedness; and no payments or distributions of cash, property or securities
to or for the benefit of the Holders pursuant to the subrogation provisions of
this Article 11, which would otherwise have been paid to the holders of Senior


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<PAGE>

Indebtedness, shall be deemed to be a payment by the Company to or for the
account of the Securities. It is understood that the provisions of this Article
11 are and are intended solely for the purposes of defining the relative rights
of the Holders, on the one hand, and the holders of the Senior Indebtedness, on
the other hand.

     Nothing contained in this Article 11 or elsewhere in this Indenture or in
the Securities is intended to or shall impair, as among the Company, its
creditors other than the holders of Senior Indebtedness, and the Holders, the
obligation of the Company, which is absolute and unconditional, to pay to the
Holders the principal of (and premium, if any), interest or Additional Interest,
if any, on the Securities as and when the same shall become due and payable in
accordance with their terms, or is intended to or shall affect the relative
rights of the Holders and creditors of the Company other than the holders of the
Senior Indebtedness, nor shall anything herein or therein prevent the Trustee or
the Holders from exercising all remedies otherwise permitted by applicable law
during the continuance of an Event of Default under this Indenture, subject to
the rights, if any, under this Article 11 of the holders of Senior Indebtedness
in respect of cash, property or securities of the Company received upon the
exercise of any such remedy.

     Upon any payment or distribution of assets of the Company referred to in
this Article 11, the Trustee, subject to the provisions of Section 8.01, and the
Holders shall be entitled to conclusively rely upon any order or decree made by
any court of competent jurisdiction in which such bankruptcy, dissolution,
winding-up, liquidation or reorganization proceedings are pending, or a
certificate of the receiver, trustee in bankruptcy, liquidating trustee, agent
or other Person making such payment or distribution, delivered to the Trustee or
to the Holders, for the purpose of ascertaining the Persons entitled to
participate in such distribution, the holders of the Senior Indebtedness and
other indebtedness of the Company, the amount thereof or payable thereon and all
other facts pertinent thereto or to this Article 11.

     Section 11.04 Authorization to Effect Subordination.

     Each Holder by accepting a Security authorizes and directs the Trustee on
such Holder's behalf to take such action as may be necessary or appropriate to
effectuate the subordination as provided in this Article 11 and as may be
requested in writing and as prepared by the holders of Senior Indebtedness at
their expense, and each Holder appoints the Trustee to act as such Holder's
attorney-in-fact for any and all such purposes. If the Trustee does not file a
proper proof of claim or proof of debt in the form required in any proceeding
referred to in Section 11.03 hereof at least 30 days before the expiration of
the time to file such claim, the holders of any Senior Indebtedness or their
Representatives are hereby authorized to file an appropriate claim for and on
behalf of the Holders and each Holder hereby appoints the holders of Senior
Indebtedness or their respective Representatives to act as its attorney-in-fact
for any and all such purposes.

     Section 11.05 Notice to Trustee.

     The Company shall give prompt written notice in the form of an Officers'
Certificate to a Responsible Officer of the Trustee and to any Paying Agent of
any fact known to the Company which would prohibit the making of any payment of
monies to or by the Trustee or any Paying Agent in respect of the Securities
pursuant to the provisions of this Article 11. Notwithstanding the provisions of
this Article 11 or any other provision of this Indenture, the Trustee shall not
be charged with knowledge of the existence of any facts which would prohibit the
making of any payment of monies to or by the Trustee in respect of the
Securities pursuant to the provisions of this Article 11, unless and until a
Responsible Officer of the Trustee shall have received written notice thereof at
the office of the Trustee specified in Section 12.02 hereof from the Company (in
the form of an Officers' Certificate) or a Representative or a holder or holders
of Senior Indebtedness; and before the receipt of any such written notice, the
Trustee, subject to the provisions of Section 8.01, shall be entitled in all
respects to assume that no such facts exist;


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<PAGE>

provided that with respect to any such monies that may become payable for any
purpose (including, without limitation, the payment of the principal of, or
premium, if any, or interest on any Security) unless the Trustee shall have
received, on a date not less than one Business Day immediately prior to the date
upon which by the terms hereof such monies shall become payable, the notice
provided for in this Section 11.05, then, anything in the first two paragraphs
of Section 11.02 contained to the contrary notwithstanding, the Trustee shall
have full power and authority to receive such monies and to apply the same to
the purpose for which they were received, and shall not be affected by any
notice to the contrary which may be received by it on or after such prior date;
provided further that if the Trustee shall receive any such notice on the date
upon which by the terms hereof such monies shall become payable, the Trustee
may, in its reasonable discretion, waive the time for notice provided in the
foregoing proviso. Nothing shall prevent any payment by the Trustee to the
holders of monies deposited with it pursuant to Article 9, and any such payment
shall not be subject to the provisions of Article 11; provided that, at the time
of any such deposit, such deposit and payment were permitted under this Article
11 without giving effect to the first clause of this sentence.

     The Trustee, subject to the provisions of Section 8.01, shall be entitled
to conclusively rely on the delivery to it of a written notice by a
Representative or a Person representing himself to be a holder of Senior
Indebtedness to establish that such notice has been given by a Representative or
a holder of Senior Indebtedness. In the event that the Trustee determines in
good faith that further evidence is required with respect to the right of any
Person as a holder of Senior Indebtedness to participate in any payment or
distribution pursuant to this Article 11, the Trustee may request such Person to
furnish evidence to the reasonable satisfaction of the Trustee as to the amount
of Senior Indebtedness held by such Person, the extent to which such Person is
entitled to participate in such payment or distribution and any other facts
pertinent to the rights of such Person under this Article 11, and if such
evidence is not furnished the Trustee may defer any payment to such Person
pending judicial determination as to the right of such Person to receive such
payment.

     Section 11.06 Trustee's Relation to Senior Indebtedness.

     The Trustee in its individual capacity shall be entitled to all the rights
set forth in this Article 11 in respect of any Senior Indebtedness at any time
held by it, to the same extent as any other holder of Senior Indebtedness, and
nothing in Section 8.11 or elsewhere in this Indenture shall deprive the Trustee
of any of its rights as such holder. Nothing in this Article 11 shall apply to
the claims of, or payment to, the Trustee under or pursuant to Section 8.07.

     With respect to the holders of Senior Indebtedness, the Trustee undertakes
to perform or to observe only such of its covenants and obligations as are
specifically set forth in this Article 11, and no implied covenants or
obligations with respect to the holders of Senior Indebtedness shall be read
into this Indenture against the Trustee. The Trustee shall not be deemed to owe
any fiduciary duty to the holders of Senior Indebtedness and, subject to the
provisions of Section 8.01, the Trustee shall not be liable to any holder of
Senior Indebtedness if it shall pay over or deliver to Holders, the Company or
any other Person money or assets to which any holder of Senior Indebtedness
shall be entitled by virtue of this Article 11 or otherwise.

     Section 11.07 No Impairment of Subordination.

     No right of any present or future holder of any Senior Indebtedness to
enforce subordination as herein provided shall at any time in any way be
prejudiced or impaired by any act or failure to act on the part of the Company
or by any act or failure to act, in good faith, by any such holder, or by any
noncompliance by the Company with the terms, provisions and covenants of this
Indenture, regardless of any knowledge thereof which any such holder may have or
otherwise be charged with.


                                       66

<PAGE>

     Section 11.08 Certain Conversions Deemed Payment.

     For the purposes of this Article 11 only, (a) the issuance and delivery of
Junior Securities upon conversion of Securities in accordance with Article 4
shall not be deemed to constitute a payment or distribution on account of the
principal of (or premium, if any), interest or Additional Interest, if any, on
the Securities or on account of the purchase or other acquisition of Securities,
and (b) the payment, issuance or delivery of cash (except in satisfaction of
fractional shares), securities (other than Junior Securities) or other property
upon conversion of a Security shall be deemed to constitute payment on account
of the principal of such Security, the payment, issuance and delivery of such
cash being made subject to the subordination provisions of this Article 11. For
the purposes of this Section 11.08, the term "Junior Securities" means (1)
shares of any stock of any class of the Company or (2) securities of the Company
which are subordinated in right of payment to all Senior Indebtedness which may
be outstanding at the time of issuance or delivery of such securities to
substantially the same extent as, or to a greater extent than, the Securities
are so subordinated as provided in this Article 11. Nothing contained in this
Article 11 or elsewhere in this Indenture or in the Securities is intended to or
shall impair, as among the Company, its creditors other than holders of Senior
Indebtedness and the Holders, the right, which is absolute and unconditional, of
the Holders to convert such Securities in accordance with Article 4.

     Section 11.09 Article Applicable to Paying Agents.

     If at any time any Paying Agent other than the Trustee shall have been
appointed by the Company and be then acting hereunder, the term "Trustee" as
used in this Article shall (unless the context otherwise requires) be construed
as extending to and including such Paying Agent within its meaning as fully for
all intents and purposes as if such Paying Agent were named in this Article in
addition to or in place of the Trustee; provided, however, that the first
paragraph of Section 11.05 shall not apply to the Company or any Affiliate of
the Company if it or such Affiliate acts as Paying Agent.

     Section 11.10 Senior Indebtedness Entitled to Rely.

     The holders of Senior Indebtedness shall have the right to rely upon this
Article 11, and no amendment or modification of the provisions of this Article
11 that adversely affect the rights and interests of such holders shall be
effective as to such holders unless such holders shall have agreed in writing
thereto. Each Holder by accepting a Security acknowledges and agrees that the
provisions of Article 11 are, and are intended to be, an inducement and
consideration to each holder of Senior Indebtedness (whether such Senior
Indebtedness was acquired or created before or after the issuance of the
Securities) to acquire and hold, or to continue to hold, such Senior
Indebtedness, and such holder of Senior Indebtedness shall be deemed
conclusively to have relied on the provisions of this Article 11 in acquiring
and continuing to hold such Senior Indebtedness.

     Section 11.11 Reinstatement.

     To the extent the payment of or distribution in respect of any Senior
Indebtedness (whether by or on behalf of the Company as proceeds of security or
enforcement of any right of setoff or otherwise) is declared to be fraudulent or
preferential, set aside or required to be paid to any receiver, trustee in
bankruptcy, liquidating trustee, agent or similar Person under any bankruptcy,
insolvency, receivership, fraudulent conveyance or similar law, then if such
payment or distribution is recovered by, or paid over to, such receiver, trustee
in bankruptcy, liquidating trustee, agent or similar Person, the Senior
Indebtedness or part thereof originally intended to be satisfied shall be deemed
to be reinstated and outstanding as if such payment had not occurred.


                                       67

<PAGE>

     Section 11.12 Actions by Holders of Senior Indebtedness.

          The holders of the Senior Indebtedness may, at any time and from time
to time, without the consent of or notice to the Trustee or the Holders, without
incurring responsibility to the Holders and without impairing or releasing the
subordination provided in this Indenture or the obligations of the Holders
hereunder to the holders of the Senior Indebtedness, do any one or more of the
following:

          (a) change the manner, place or terms of payment or extend the time of
     payment of, or renew or alter, the Senior Indebtedness or any instrument
     evidencing the same or any agreement under which any Senior Indebtedness is
     outstanding or secured;

          (b) sell, exchange, release or otherwise deal with any property
     pledged, mortgaged or otherwise secured;

          (c) release any Person liable in any manner for the collection of
     Senior Indebtedness;

          (d) exercise or refrain from exercising any rights against the Company
     or any other Person; and

          (e) take any other action in the reasonable business judgment of the
     holders of Senior Indebtedness.


                                       68

<PAGE>

                                   ARTICLE 12

                                  MISCELLANEOUS

     Section 12.01 Trust Indenture Act Controls.

     If any provision of this Indenture limits, qualifies or conflicts with the
duties imposed by any of Sections 310 to 317, inclusive, of the TIA through
operation of Section 318(c) thereof, such imposed duties shall control.

     Section 12.02 Notices.

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

               If to the Company, to:

               SPSS Inc.
               233 S. Wacker Drive, 11th Floor
               Chicago, IL 60606
               Attention: Chief Financial Officer
               Tel: 312-651-3000
               Fax: (312) 651-3668

               with a copy to:

               Mayer, Brown, Rowe & Maw LLP
               71 S. Wacker Drive
               Chicago, IL 60606
               Attention: David A. Schuette
               Tel: (312) 701-7363
               Fax: (312) 706-8201

               if to the Trustee, to:

               LaSalle Bank National Association
               135 S. LaSalle Street, Suite 1560
               Chicago, Illinois 60603
               Attention: Gregory S. Clarke (SPSS Inc. 2.50% Convertible
                          Subordinated Notes due 2012)
               Tel: (312) 904-5532
               Fax: (312) 904-4018

     Such notices or communications shall be effective when received.

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


                                       69

<PAGE>

     Any notice or communication mailed to a Holder of a Security shall be
mailed by first-class mail or delivered by an overnight delivery service to it
at its address shown on the register kept by the Primary Registrar.

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

     If the Company mails any notice to a Holder of a Security, it shall mail a
copy to the Trustee and each Registrar, Paying Agent and Conversion Agent.

     Section 12.03 Communications By Holders with Other Holder.

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

     Section 12.04 Certificate and Opinion as to Conditions Precedent.

     (a) 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 at the
request of the Trustee:

          (1) an Officers' Certificate stating that, in the opinion of the
     signers, all conditions precedent (including any covenants, compliance with
     which constitutes a condition 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 (including any covenants, compliance
     with which constitutes a condition precedent) have been complied with.

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

          (1) a statement that the person making such certificate or opinion 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
     certificate or opinion are based;

          (3) a statement that, in the opinion of such person, 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 as to whether or not, in the opinion of such person,
     such condition or covenant has been complied with;

provided, however, that with respect to matters of fact an Opinion of Counsel
may rely on an Officers' Certificate or certificates of public officials.

     Section 12.05 Record Date for Vote or Consent of Holders of Securities.


                                       70

<PAGE>

     The Company (or, in the event deposits have been made pursuant to Section
9.01, the Trustee) 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 not be
more than 30 days prior to the date of the commencement of solicitation of such
action. Notwithstanding the provisions of Section 10.04, if a record date is
fixed, those persons who were Holders of Securities at the close of business on
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 12.06 Rules by Trustee, Paying Agent, Registrar and Conversion
Agent.

     The Trustee may make reasonable rules (not inconsistent with the terms of
this Indenture) for action by or at a meeting of Holders. Any Registrar, Paying
Agent or Conversion Agent may make reasonable rules for its functions.

     Section 12.07 Legal Holidays.

     A "Legal Holiday" is a Saturday, Sunday or a day on which state or
federally chartered banking institutions in New York, New York or Chicago,
Illinois are authorized or obligated to close. If a payment date is a Legal
Holiday, payment shall be made on the next succeeding day that is not a Legal
Holiday, and no interest shall accrue for the intervening period. If a Regular
Record Date is a Legal Holiday, the record date shall not be affected.

     Section 12.08 Governing Law.

     This Indenture and the Securities shall be governed by, and construed in
accordance with, the laws of the State of New York.

     Section 12.09 No Adverse Interpretation of Other Agreements.

     This Indenture may not be used to interpret another indenture, loan or debt
agreement of the Company or a Subsidiary of the Company. Any such indenture,
loan or debt agreement may not be used to interpret this Indenture.

     Section 12.10 No Recourse Against Others.

     All liability described in paragraph 15 of the Securities of any director,
officer, employee or shareholder, as such, of the Company hereby is waived and
released by each of the Holders.

     Section 12.11 No Security Interest Created.

     Nothing in this Indenture or in the Securities, express or implied, shall
be construed to constitute a security interest under the Uniform Commercial Code
or similar legislation, now in effect or hereafter enacted and made effective,
in any jurisdiction.

     Section 12.12 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 12.13 Multiple Counterparts.


                                       71

<PAGE>

     The parties may sign multiple counterparts of this Indenture. Each signed
counterpart shall be deemed an original, but all of them together represent the
same agreement.

     Section 12.14 Separability.

     If any provisions 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 12.15 Table of Contents, Headings, Etc.

     The table of contents, cross-reference sheet and headings of the Articles
and Sections of this Indenture have been inserted for convenience of reference
only, are not to be considered a part hereof, and shall in no way modify or
restrict any of the terms or provisions hereof.

                            [SIGNATURE PAGE FOLLOWS]


                                       72

<PAGE>

     IN WITNESS WHEREOF, the parties hereto have hereunto set their hands as of
the date and year first above written.

                                        SPSS INC.


                                        By: /s/ Raymond H. Panza
                                            ------------------------------------
                                        Name: Raymond H. Panza
                                        Title: EVP-CFO


                                        LASALLE BANK NATIONAL ASSOCIATION


                                        By: /s/ Gregory S. Clarke
                                            ------------------------------------
                                        Name: Gregory S. Clarke
                                        Title: Vice President
<PAGE>

                                    EXHIBIT A

                           [FORM OF FACE OF SECURITY]

     UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY TO THE COMPANY OR ITS AGENT FOR REGISTRATION OF
TRANSFER, 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 THE DEPOSITORY TRUST COMPANY (AND ANY PAYMENT HEREON IS MADE
TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY), ANY TRANSFER, PLEDGE OR OTHER
USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE THE
REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN. THIS SECURITY IS A
GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND
IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE THEREOF. THIS SECURITY IS
EXCHANGEABLE FOR SECURITIES REGISTERED IN THE NAME OF A PERSON OTHER THAN THE
DEPOSITARY OR ITS NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE
INDENTURE AND, UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR
SECURITIES IN DEFINITIVE FORM, THIS SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A
WHOLE 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.(1)

     THIS SECURITY AND THE SHARES OF COMMON STOCK ISSUABLE UPON CONVERSION OF
THIS SECURITY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED (THE "SECURITIES ACT"), OR ANY STATE SECURITIES LAWS. NEITHER THIS
SECURITY, THE SHARES OF COMMON STOCK ISSUABLE UPON CONVERSION OF THIS SECURITY
NOR ANY INTEREST OR PARTICIPATION HEREIN OR THEREIN MAY BE REOFFERED, SOLD,
ASSIGNED, TRANSFERRED, PLEDGED, ENCUMBERED OR OTHERWISE DISPOSED OF IN THE
ABSENCE OF SUCH REGISTRATION OR UNLESS SUCH TRANSACTION IS EXEMPT FROM, OR NOT
SUBJECT TO, REGISTRATION UNDER THE SECURITIES ACT.(2)

     BY ITS ACQUISITION HEREOF, THE HOLDER AGREES TO OFFER, SELL OR OTHERWISE
TRANSFER SUCH SECURITY PRIOR TO THE DATE THAT IS TWO YEARS AFTER THE LATER OF
THE ORIGINAL ISSUE DATE HEREOF AND THE LAST DATE ON WHICH SPSS INC. (THE
"COMPANY") OR ANY AFFILIATE OF THE COMPANY WAS THE OWNER OF THIS SECURITY (OR
ANY PREDECESSOR OF SUCH SECURITY) (THE "RESALE RESTRICTION TERMINATION DATE")
ONLY (A) TO THE COMPANY OR ANY SUBSIDIARY THEREOF, (B) PURSUANT TO A
REGISTRATION STATEMENT WHICH HAS BEEN DECLARED EFFECTIVE UNDER THE SECURITIES
ACT, (C) FOR SO LONG AS THE SECURITIES ARE ELIGIBLE FOR RESALE PURSUANT TO RULE
144A, TO A PERSON IT REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL BUYER AS
DEFINED IN RULE 144A THAT

----------
(1)  This paragraph should be included only if the Security is a Global
     Security.

(2)  These paragraphs to be included only if the Security is a Restricted
     Security.


                                       A-1

<PAGE>

PURCHASES FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A
QUALIFIED INSTITUTIONAL BUYER TO WHOM NOTICE IS GIVEN THAT THE TRANSFER IS BEING
MADE IN RELIANCE ON RULE 144A, OR (D) PURSUANT TO ANY OTHER AVAILABLE EXEMPTION
FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT, SUBJECT TO THE
COMPANY'S AND THE TRUSTEE'S RIGHT PRIOR TO ANY SUCH OFFER, SALE OR TRANSFER
PURSUANT TO CLAUSE (D) PRIOR TO THE RESALE RESTRICTION TERMINATION DATE TO
REQUIRE THE DELIVERY OF AN OPINION OF COUNSEL, CERTIFICATIONS AND/OR OTHER
INFORMATION SATISFACTORY TO EACH OF THEM, AND IN EACH OF THE FOREGOING CASES, TO
REQUIRE THAT A CERTIFICATE OF TRANSFER IN THE FORM APPEARING ON THE OTHER SIDE
OF THIS SECURITY IS COMPLETED AND DELIVERED BY THE TRANSFEROR TO THE TRUSTEE.
THIS LEGEND WILL BE REMOVED UPON THE REQUEST OF THE HOLDER AFTER THE RESALE
RESTRICTION TERMINATION DATE.(2)

     THE HOLDER OF THIS SECURITY IS ENTITLED TO THE BENEFITS OF A REGISTRATION
RIGHTS AGREEMENT (AS SUCH TERM IS DEFINED IN THE INDENTURE REFERRED TO ON THE
REVERSE HEREOF) AND, BY ITS ACCEPTANCE HEREOF, AGREES TO BE BOUND BY AND TO
COMPLY WITH THE PROVISIONS OF SUCH REGISTRATION RIGHTS AGREEMENT.(2)


                                      A-2

<PAGE>

                                    SPSS INC.
                  2.50% Convertible Subordinated Notes due 2012

No. ______                                                         CUSIP: ______

     SPSS Inc., a Delaware corporation, promises to pay to Cede & Co. or
registered assigns the principal amount of one hundred fifty million dollars
($150,000,000) on March 15, 2012.

     This Security shall bear interest 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.

Dated: ____________, 2007

                            [SIGNATURE PAGE FOLLOWS]


                                      A-3

<PAGE>

     IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

                                        SPSS INC.


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

Dated: __________, 2007

Trustee's Certificate of Authentication:
This is one of the Securities referred
to in the within-mentioned Indenture.

LASALLE BANK NATIONAL ASSOCIATION
   as Trustee


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


                                      A-4

<PAGE>

                       [FORM OF REVERSE SIDE OF SECURITY]

                                    SPSS INC.
                  2.50% CONVERTIBLE SUBORDINATED NOTES DUE 2012

1. INTEREST

     SPSS Inc., a Delaware corporation (the "Company", which term shall include
any successor corporation under the Indenture hereinafter referred to), promises
to pay interest on the principal amount of this Security at the rate of 2.50%
per annum. The Company shall pay interest semiannually on March 15 and September
15 of each year (each, an "Interest Payment Date"), commencing September 15,
2007. Each payment of interest will include interest accrued through the day
before the relevant Interest Payment Date (or purchase date). Cash interest will
be computed on the basis of a 360-day year comprised of twelve 30-day months.
Any payment required to be made on a day that is not a Business Day shall be
made on the next succeeding Business Day. Any reference herein to interest
accrued or payable as of any date shall include any Additional Interest accrued
or payable on such date as provided in the Registration Rights Agreement.

     No sinking fund is provided for the Securities.

2. METHOD OF PAYMENT

     The Company shall pay interest on this Security (except defaulted interest)
to the person who is the Holder of this Security at the close of business on
March 1 or September 1, as the case may be (each, a "Regular Record Date"), next
preceding the related Interest Payment Date. The Holder must surrender this
Security to a Paying Agent to collect payment of principal. The Company will pay
principal and interest in money of the United States that at the time of payment
is legal tender for payment of public and private debts. The Company may pay
principal and interest in respect of any Certificated Security by check or wire
payable in such money; provided, however, that a Holder with an aggregate
principal amount in excess of $2,000,000 will be paid by wire transfer in
immediately available funds at the election of such Holder if such Holder has
provided wire transfer instructions to the Trustee at least 10 Business Days
prior to the Payment Date. The Company may mail an interest check to the
Holder's registered address. Notwithstanding the foregoing, so long as this
Security is registered in the name of a Depositary or its nominee, all payments
hereon shall be made by wire transfer of immediately available funds to the
account of the Depositary or its nominee.

     Any wire transfer instructions received by the Trustee will remain in
effect until revoked by the Holder.

3. PAYING AGENT, REGISTRAR AND CONVERSION AGENT

     Initially, LaSalle Bank National Association (the "Trustee", which term
shall include any successor trustee under the Indenture hereinafter referred to)
will act as Paying Agent, Registrar and Conversion Agent. The Company may change
any Paying Agent, Registrar or Conversion Agent without notice to the Holder.
The Company or any of its Subsidiaries may, subject to certain limitations set
forth in the Indenture, act as Paying Agent or Registrar.

4. INDENTURE, LIMITATIONS

     This Security is one of a duly authorized issue of Securities of the
Company designated as its 2.50% Convertible Subordinated Notes due 2012 (the
"Securities"), issued under an Indenture dated as of


                                      A-5

<PAGE>

March 19, 2007 (together with any supplemental indentures thereto, the
"Indenture"), between the Company and the Trustee. The terms of this Security
include those stated in the Indenture and those required by or made part of the
Indenture by reference to the Trust Indenture Act of 1939, as amended, as in
effect on the date of the Indenture. This Security is subject to all such terms,
and the Holder of this security is referred to the Indenture and said Act for a
statement of them. Capitalized terms not otherwise defined herein have the
meaning ascribed to such terms in the Indenture.

     The Securities are unsecured, subordinated obligations of the Company
limited to $150,000,000 aggregate principal amount. The Indenture does not limit
other debt of the Company, secured or unsecured.

5. PURCHASE OF SECURITIES OF HOLDERS' OPTION UPON A FUNDAMENTAL CHANGE

     If a Fundamental Change occurs prior to the Final Maturity Date, at the
option of the Holder and subject to the terms and conditions of the Indenture,
the Company shall become obligated to purchase for cash all or any part
specified by the Holder (so long as the principal amount of such part is $1,000
or an integral multiple of $1,000) of the Securities held by such Holder on a
date specified by the Company that is not less than 30 nor more than 45 days
after the date of the Fundamental Change Company Notice, at a purchase price
equal to 100% of the principal amount thereof together with accrued and unpaid
interest, if any, and accrued and unpaid Additional Interest, if any, to, but
excluding, the Fundamental Change Purchase Date. The Holder shall have the right
to withdraw any Fundamental Change Purchase Notice (in whole or in a portion
thereof that is $1,000 or an integral multiple of $1,000) at any time prior to
the close of business on the Business Day next preceding the Fundamental Change
Purchase Date by delivering a written notice of withdrawal to the Paying Agent
in accordance with the terms of the Indenture.

6. CONVERSION

     Subject to and upon compliance with the provisions of the Indenture and
upon the occurrence of the events specified in the Indenture, a Holder may
surrender for conversion any Security that is $1,000 principal amount or
integral multiples thereof. Unless the Company has made a Physical Settlement
Election, in lieu of receiving shares of Common Stock, a Holder will receive,
for each $1,000 principal amount of Securities surrendered for conversion:

     -    cash in an amount equal to the lesser of (1) $1,000 and (2) the
          Conversion Value; and

     -    if the Conversion Value is greater than $1,000, a number of shares of
          Common Stock equal to the sum of the Daily Share Amounts, for each of
          the fifteen consecutive Trading Days in the Conversion Reference
          Period, appropriately adjusted to reflect stock splits, stock
          dividends, combinations or similar events occurring during the
          Conversion Reference Period, subject to the Company's right to deliver
          cash in lieu of all or a portion of such shares as described in the
          Indenture;

provided that in no event shall the aggregate number of shares of Common Stock
to be issued pursuant to the foregoing clause, per $1,000 principal amount of
Securities, exceed the Aggregate Share Cap, as defined in the Indenture, without
taking into account any election by the Company to deliver cash in lieu of all
or a portion of the shares of Common Stock otherwise deliverable as set forth in
the Indenture.

     The Conversion Rate on any Securities surrendered in connection with a
Fundamental Change may be increased by an amount, if any, determined in
accordance with Section 4.01(j) of the Indenture.


                                      A-6

<PAGE>

7. SUBORDINATION

     To the extent provided in the Indenture, the Securities are subordinated to
Senior Indebtedness, as defined in the Indenture, of the Company. To the extent
provided in the Indenture, Senior Indebtedness must be paid in full before the
Securities may be paid. The Company agrees, and each Securityholder by accepting
a Security agrees, to the subordination provisions contained in the Indenture
and authorizes the Trustee to give it effect and appoints the Trustee as
attorney-in-fact for such purpose.

8. DENOMINATIONS, TRANSFER, EXCHANGE

     The Securities are in registered form, without coupons, in denominations of
$1,000 principal amount and integral multiples of $1,000 principal amount. A
Holder may register the transfer of or exchange Securities in accordance with
the Indenture. The Registrar may require a Holder, among other things, to
furnish appropriate endorsements and transfer documents.

9. PERSONS DEEMED OWNERS

     The Holder of a Security may be treated as the owner of it for all
purposes.

10. UNCLAIMED MONEY

     If money for the payment of principal or interest remains unclaimed for two
years, the Trustee and any Paying Agent will pay the money back to the Company
at its written request, subject to applicable unclaimed property law and the
provisions of the Indenture. After that, Holders entitled to money must look to
the Company for payment as general creditors unless an applicable abandoned
property law designates another person.

11. AMENDMENT, SUPPLEMENT AND WAIVER

     Subject to certain exceptions, the Indenture or the Securities may be
amended or supplemented with the consent of the Holders of at least a majority
in aggregate principal amount of the Securities then outstanding, and an
existing Default or Event of Default and its consequence or compliance with any
provision of the Indenture or the Securities may be waived in a particular
instance with the consent of the Holders of a majority in aggregate principal
amount of the Securities then outstanding. Without the consent of or notice to
any Holder, the Company and the Trustee may amend or supplement the Indenture or
the Securities to, among other things, cure any ambiguity, defect or
inconsistency or make any other change that does not adversely affect the rights
of the Holders in any material respect.

12. SUCCESSOR ENTITY

     When a successor corporation assumes all the obligations of its predecessor
under the Securities and the Indenture in accordance with the terms and
conditions of the Indenture, the predecessor corporation (except in certain
circumstances specified in the Indenture) shall be released from those
obligations.

13. DEFAULTS AND REMEDIES

     Under the Indenture, an Event of Default shall occur if:

          (1) the Company shall fail to pay when due the Principal or
     Fundamental Change Purchase Price of any Security, when the same becomes
     due and payable whether at the Final


                                      A-7

<PAGE>

     Maturity Date, upon repurchase, acceleration or otherwise and regardless of
     whether such payment is permitted pursuant to the subordination provisions
     under Article 11 of the Indenture; or

          (2) the Company shall fail to pay an installment of cash interest or
     Additional Interest, if any, on any of the Securities, which failure
     continues for 30 days after the date when due, regardless of whether such
     payment is permitted pursuant to the subordination provisions under Article
     11 of the Indenture; or

          (3) the Company shall fail to deliver when due all cash and shares of
     Common Stock, if any, deliverable upon conversion of Securities in excess
     of 25% in aggregate principal amount of the Securities then outstanding,
     which failure continues for 15 days, regardless of whether such payment is
     permitted pursuant to the subordination provisions under Article 11 of the
     Indenture; or

          (4) the Company shall fail to perform or observe (or obtain a waiver
     with respect to) any other term, covenant or agreement contained in the
     Securities or the Indenture for a period of 60 days after receipt by the
     Company of a Notice of Default specifying such failure; or

          (5) default in the payment of principal by the end of any applicable
     grace period or resulting in acceleration of other Indebtedness of the
     Company for borrowed money where the aggregate principal amount with
     respect to which the default or acceleration has occurred exceeds $15
     million and such acceleration has not been rescinded or annulled or such
     Indebtedness repaid within a period of 30 days after receipt by the Company
     of a Notice of Default, provided that if any such default is cured, waived,
     rescinded or annulled, then the Event of Default by reason thereof would be
     deemed not to have occurred; or

          (6) the Company, or any Significant Subsidiary of the Company,
     pursuant to or within the meaning of any Bankruptcy Law:

               (A) commences as a debtor a voluntary case or proceeding; or

               (B) consents to the entry of an order for relief against it in an
          involuntary case or proceeding or the commencement of any case against
          it;

               (C) consents to the appointment of a Receiver of it or for all or
          substantially all of its property; or

               (D) makes a general assignment for the benefit of its creditors;

               (E) files a petition in bankruptcy or answer or consent seeking
          reorganization or relief; or

               (F) consents to the filing of such a petition or the appointment
          of or taking possession by a Receiver; or

          (7) a court of competent jurisdiction enters an order or decree under
     any Bankruptcy Law that:


                                      A-8

<PAGE>

               (A) grants relief against the Company or any Significant
          Subsidiary of the Company in an involuntary case or proceeding or
          adjudicates the Company or any Significant Subsidiary of the Company
          insolvent or bankrupt;

               (B) appoints a Receiver of the Company or any Significant
          Subsidiary of the Company or for all or substantially all of the
          property of the Company or any Significant Subsidiary of the Company;
          or

               (C) orders the winding up or liquidation of the Company or any
          Significant Subsidiary of the Company;

and in each case the order or decree remains unstayed and in effect for 60
consecutive days.

     The term "Bankruptcy Law" means Title 11 of the United States Code (or any
successor thereto) or any similar federal or state law for the relief of
debtors. The term "Receiver" means any receiver, trustee, assignee, liquidator,
sequestrator or similar official under any Bankruptcy Law.

     Notwithstanding the above, no Event of Default under clauses (4) or (5)
above shall occur until the Trustee notifies the Company in writing, or the
Holders of at least 25% in aggregate principal amount of the Securities then
outstanding notify the Company and the Trustee in writing, of the Default (a
"Notice of Default"), and the Company does not cure the Default within the time
specified in clause (4) or (5), as applicable, after receipt of such notice.

     If an Event of Default (other than an Event of Default specified in clause
(6) or (7) above) occurs and is continuing with respect to the Company, the
Trustee may, by notice to the Company, or the Holders of at least 25% in
aggregate principal amount of the Securities then outstanding may, by notice to
the Company and the Trustee, declare the principal amount and accrued and unpaid
interest, if any, and accrued and unpaid Additional Interest, if any, through
the date of declaration on all the Securities to be immediately due and payable.
Upon such a declaration, such principal amount and such accrued and unpaid
interest, if any, and such accrued and unpaid Additional Interest, if any, shall
be due and payable immediately. If an Event of Default specified in clauses (6)
or (7) above occurs in respect of the Company and is continuing, the principal
amount and accrued but unpaid interest, if any, and accrued and unpaid
Additional Interest, if any, 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 of Securities The Holders of a majority in aggregate
principal amount of the Securities then outstanding by notice to the Trustee may
rescind an acceleration and its consequences if (a) all existing Events of
Default, other than the nonpayment of the principal of the Securities which have
become due solely by such declaration of acceleration, have been cured or
waived; (b) to the extent the payment of such interest is lawful, interest
(calculated at the rate per annum borne by the Securities) on overdue
installments of interest and overdue principal, which has become due otherwise
than by such declaration of acceleration, has been paid; (c) the rescission
would not conflict with any judgment or decree of a court of competent
jurisdiction; and (d) all payments due to the Trustee and any predecessor
Trustee under the Indenture have been made. No such rescission shall affect any
subsequent Default or impair any right consequent thereto.

     Holders may not enforce the Indenture or the Securities except as provided
in the Indenture. The Trustee may require indemnity satisfactory to it before it
enforces the Indenture or the Securities. Subject to certain limitations,
Holders of a majority in aggregate principal amount of the Securities then
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 principal or interest) if and so long as it determines
that withholding notice is in their interests. The Company is required to file
periodic


                                      A-9

<PAGE>

certificates with the Trustee as to the Company's compliance with the Indenture
and knowledge or status of any Default.

14. TRUSTEE DEALINGS WITH THE COMPANY

     LaSalle Bank National Association, the initial Trustee under the Indenture,
in its individual or any other capacity, may make loans to, accept deposits from
and perform services for the Company or an Affiliate of the Company, and may
otherwise deal with the Company or an Affiliate of the Company, as if it were
not the Trustee.

15. NO RECOURSE AGAINST OTHERS

     A director, officer, employee or shareholder, as such, of the Company shall
not have any liability for any obligations of the Company under the Securities
or the Indenture nor for any claim based on, in respect of or by reason of such
obligations or their creation. The Holder of this Security by accepting this
Security waives and releases all such liability. The waiver and release are part
of the consideration for the issuance of this Security.

16. AUTHENTICATION

     This Security shall not be valid until the Trustee or an authenticating
agent manually signs the certificate of authentication on the other side of this
Security.

17. ABBREVIATIONS AND DEFINITIONS

     Customary abbreviations may be used in the name of the Holder or an
assignee, such as: TEN COM (= tenants in common), TEN ENT (= tenants by the
entireties), JT TEN (= joint tenants with right of survivorship and not as
tenants in common), CUST (= Custodian) and UGMA (= Uniform Gifts to Minors Act).

     All terms defined in the Indenture and used in this Security but not
specifically defined herein are defined in the Indenture and are used herein as
so defined.

18. INDENTURE TO CONTROL; GOVERNING LAW

     In the case of any conflict between the provisions of this Security and the
Indenture, the provisions of the Indenture shall control. This Security and the
Indenture shall be governed by, and construed in accordance with, the laws of
the State of New York.

     The Company will furnish to any Holder, upon written request and without
charge, a copy of the Indenture. Requests may be made to: SPSS Inc., 233 South
Wacker Drive, 11th Floor, Chicago, Illinois 60606, Attention: Chief Financial
Officer, Telephone: (312) 651-3000.


                                      A-10

<PAGE>

                                 ASSIGNMENT FORM

     To assign this Security, fill in the form below:

     I or we assign and transfer this Security to

_______________________________________________________________________________
                  (Insert assignee's soc. sec. or tax I.D. no.)

_______________________________________________________________________________

_______________________________________________________________________________

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

and irrevocably appoint

_______________________________________________________________________________
agent to transfer this Security on the books of the Company. The agent may
substitute another to act for him or her.

                                        Your Signature



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

*    Signature guaranteed by:


By:
    ---------------------------------

----------
*    The signature must be guaranteed by an institution which is a member of one
     of the following recognized signature guaranty programs: (i) the Securities
     Transfer Agent Medallion Program (STAMP); (ii) the New York Stock Exchange
     Medallion Program (MSP); (iii) the Stock Exchange Medallion Program (SEMP);
     or (iv) such other guaranty program acceptable to the Trustee.


                                      A-11

<PAGE>

                                CONVERSION NOTICE

     To convert this Security into Common Stock of the Company, check the box:

[ ]  To convert only part of this Security, state the principal amount to be
     converted (must be $1,000 or a integral multiple of $1,000): $__________.

[ ]  If you want the stock certificate made out in another person's name, fill
     in the form below:

_______________________________________________________________________________
                  (Insert assignee's soc. sec. or tax I.D. no.)

_______________________________________________________________________________

_______________________________________________________________________________

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

                                        Your Signature

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

*    Signature guaranteed by:


By:
    ---------------------------------

----------
*    The signature must be guaranteed by an institution which is a member of one
     of the following recognized signature guaranty programs: (i) the Securities
     Transfer Agent Medallion Program (STAMP); (ii) the New York Stock Exchange
     Medallion Program (MSP); (iii) the Stock Exchange Medallion Program (SEMP);
     or (iv) such other guaranty program acceptable to the Trustee.


                                      A-12

<PAGE>

                      FUNDAMENTAL CHANGE REPURCHASE NOTICE

To: SPSS Inc.

     The undersigned registered owner of this Security hereby irrevocably
acknowledges receipt of a notice from SPSS Inc. (the "Company") as to the
occurrence of a Fundamental Change with respect to the Company and requests and
instructs the Company to purchase the entire principal amount of this Security,
or the portion thereof (which is $1,000 or an integral multiple thereof) below
designated, in accordance with the terms of the Security and the Indenture
referred to in the Security at the Fundamental Change Purchase Price, together
with accrued and unpaid interest and Additional Interest, if any, to, but
excluding, such date, to the registered Holder hereof.


Date:
      -------------------------------   ----------------------------------------
                                        Signature (s)

                                        Signature(s) must be guaranteed by a
                                        qualified guarantor institution with
                                        membership in an approved signature
                                        guarantee program pursuant to Rule
                                        17Ad-15 under the Securities Exchange
                                        Act of 1934.


                                        ----------------------------------------
                                        Signature Guaranty

Principal amount to be purchased (in
an integral multiple of $1,000, if
less than all):
                --------------------

----------
NOTICE: The signature to the foregoing Election must correspond to the Name as
written upon the face of this Security in every particular, without any
alteration or change whatsoever.


                                      A-13

<PAGE>

                     SCHEDULE OF EXCHANGES OF SECURITIES(1)

     The following exchanges, purchases or conversions of a part of this Global
Security have been made:

<TABLE>
<CAPTION>
 Principal Amount of this Global                              Amount of Decrease in       Amount of Increase in
Security Following Such Decrease   Authorized Signatory of   Principal Amount of this   Principal Amount of this
 Date of Exchange (or Increase)      Securities Custodian        Global Security             Global Security
--------------------------------   -----------------------   ------------------------   ------------------------
<S>                                <C>                       <C>                        <C>

</TABLE>

----------
1.   This schedule should be included only if the Security is a Global Security.


                                      A-14

<PAGE>

            CERTIFICATE TO BE DELIVERED UPON EXCHANGE OR REGISTRATION
                      OF TRANSFER OF RESTRICTED SECURITIES

Re:  2.50% Convertible Subordinated Notes due 2012 (the "Securities") of SPSS
     Inc.

     This certificate relates to $________ principal amount of Securities owned
in (check applicable box)

_______ book-entry or _______ definitive form by _____________________ (the
"Transferor").

     The Transferor has requested a Registrar or the Trustee to exchange or
register the transfer of such Securities.

     In connection with such request and in respect of each such Security, the
Transferor does hereby certify that the Transferor is familiar with transfer
restrictions relating to the Securities as provided in Section 2.12 of the
Indenture dated as of March 19, 2007 between SPSS Inc. and LaSalle Bank National
Association, as trustee (the "Indenture"), and the transfer of such Security is
being made pursuant to an effective registration statement under the Securities
Act of 1933, as amended (the "Securities Act") (check applicable box), or the
transfer or exchange, as the case may be, of such Security does not require
registration under the Securities Act because (check applicable box):

[ ]  Such Security is being transferred pursuant to an effective registration
     statement under the Securities Act.

[ ]  Such Security is being acquired for the Transferor's own account, without
     transfer.

[ ]  Such Security is being transferred to the Company or a Subsidiary (as
     defined in the Indenture) of the Company.

[ ]  Such security is being transferred to a person the Transferor reasonably
     believes is a "qualified institutional buyer" (as defined in Rule 144A or
     any successor provision thereto ("Rule 144A") under the Securities Act)
     that is purchasing for its own account or for the account of a "qualified
     institutional buyer", in each case to whom notice has been given that the
     transfer is being made in reliance on such Rule 144A, and in each case in
     reliance on Rule 144A.

[ ]  Such Security is being transferred pursuant to and in compliance with an
     exemption from the registration requirements under the Securities Act in
     accordance with Rule 144 (or any successor thereto) ("Rule 144") under the
     Securities Act.

[ ]  Such Security is being transferred to a non-U.S. Person in an offshore
     transaction in compliance with Rule 904 of Regulation S under the
     Securities Act (or any successor thereto).

[ ]  Such Security is being transferred pursuant to and in compliance with an
     exemption from the registration requirements of the Securities Act (other
     than an exemption referred to above) and as a result of which such Security
     will, upon such transfer, cease to be a "restricted security" within the


                                      A-15

<PAGE>

     meaning of Rule 144 under the Securities Act.

     The Transferor acknowledges and agrees that, if the transferee will hold
any such Securities in the form of beneficial interests in a Global Security
which is a "restricted security" within the meaning of Rule 144 under the
Securities Act, then such transfer can only be made pursuant to (i) Rule 144A
under the Securities Act and such transferee must be a "qualified institutional
buyer" (as defined in Rule 144A) or (ii) Regulation S under the Securities Act.


Date:
      -------------------------------   ----------------------------------------
                                               (Insert Name of Transferor)


                                      A-16