<PAGE>   1
                                                                   EXHIBIT 4.03



                                   ENRON CORP.


                                 $1,907,698,000


                  Zero Coupon Convertible Senior Notes due 2021







                          REGISTRATION RIGHTS AGREEMENT






                                February 7, 2001









<PAGE>   2

                                TABLE OF CONTENTS
<TABLE>
<CAPTION>

                                                                                                               PAGE
                                                                                                               ----
<S>                                                                                                              <C>
1.  Certain Definitions...........................................................................................3
2.  Registration Under the Securities Act.........................................................................6
3.  Registration Procedures.......................................................................................9
4.  Holder's Obligations.........................................................................................14
5.  Registration Expenses........................................................................................14
6.  Representations and Warranties...............................................................................15
7.  Indemnification..............................................................................................17
8.  Rule 144.....................................................................................................19
9.  Miscellaneous................................................................................................20
</TABLE>


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<PAGE>   3



                                   ENRON CORP.

                  Zero Coupon Convertible Senior Notes due 2021

                          Registration Rights Agreement


                                                              New York, New York
                                                                February 7, 2001

Salomon Smith Barney Inc.
J.P. Morgan Securities Inc.
Deutsche Banc Alex. Brown Inc.
Banc of America Securities LLC
Barclays Capital Inc.
c/o Salomon Smith Barney Inc.
388 Greenwich Street
New York, New York  10013

Ladies and Gentlemen:

                  Enron Corp., an Oregon corporation (the "Issuer"), proposes to
issue and sell to the several purchasers (the "Initial Purchasers"),
$1,907,698,000 principal amount at maturity of its Zero Coupon Convertible
Senior Notes due 2021 (the "Firm Notes"), upon the terms set forth in a purchase
agreement, dated January 31, 2001 (the "Purchase Agreement"), relating to the
initial placement of the Firm Notes and the grant from the Issuer to the Initial
Purchasers of an option to purchase up to $381,540,000 additional principal
amount at maturity of such notes to cover over-allotments, if any (together with
the Firm Notes, the "Notes"). The Notes are to be issued under an indenture (the
"Indenture"), dated as of even date herewith, between the Issuer and The Chase
Manhattan Bank, as trustee (the "Trustee"). To induce the Initial Purchasers to
enter into the Purchase Agreement, the Issuer agreed in the Purchase Agreement
to enter into this registration rights agreement (this "Agreement"), with the
Initial Purchasers, under which the Issuer agrees with the Initial Purchasers
for their benefit and the benefit of the holders from time to time of the Notes
or the shares of common stock of the Issuer issuable upon conversion of the
Notes (including, without limitation, the Initial Purchasers) (each a "Holder"
and, together, the "Holders"), as follows:

         1. Certain Definitions. The following terms, when used in this
Agreement, shall have the meanings indicated:

                  (a) "Applicable Conversion Price" shall mean, as of any date
         of determination, the Applicable Principal Amount as of such date of
         determination divided by the Conversion Rate in effect as of such date
         of determination or, if no Notes are then outstanding, the Conversion
         Rate that would be in effect were Notes then outstanding.

                  (b) "Applicable Principal Amount" shall mean, as of any date
         of determination, with respect to each $1,000 principal amount at
         maturity of Notes outstanding, (i) the sum of the Issue Price (as
         defined in the Indenture) of such Notes ($655.24) plus accrued Original
         Issue Discount (as defined in the Indenture) with respect



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         to such Notes through such date of determination or, if no Notes are
         then outstanding, such sum calculated as if Notes were then
         outstanding, or (ii) if the Notes have been converted to semiannual
         coupon notes upon a Tax Event (as defined in the Indenture) pursuant to
         Section 10 of the Indenture, the Restated Principal Amount (as defined
         in the Indenture).

                  (c) "Business Day" shall mean any day other than a Saturday, a
         Sunday or a legal holiday or a day on which banking institutions or
         trust companies are authorized or obligated by law to close either in
         the State of New York or the State of Texas.

                  (d) "Closing Date" shall mean February 7, 2001, the original
         date of issuance of the Notes.

                  (e) "Commission" shall mean the Securities and Exchange
         Commission.

                  (f) "Common Stock" shall mean the Issuer's common stock.

                  (g) "Conversion Rate" shall have the meaning indicated in the
         Indenture.

                  (h) "Damages Payment Date" shall have the meaning set forth in
         Section 2(f).

                  (i) "Deferral Notice" shall have the meaning indicated in
         Section 3(g).

                  (j) "Deferral Period" shall have the meaning indicated in
         Section 3(g).

                  (k) "Effective Time" shall mean the time and date as of which
         the Commission declares the Shelf Registration effective or as of which
         the Shelf Registration otherwise becomes effective.

                  (l) "Exchange Act" shall mean the Securities Exchange Act of
         1934, as amended, and the rules and regulations of the Commission
         promulgated thereunder.

                  (m) "Firm Notes" shall have the meaning indicated in the
         introductory paragraph.

                  (n) "Holder" and "Holders" shall have the meanings indicated
         in the introductory paragraph.

                  (o) "Indenture" shall have the meaning indicated in the
         introductory paragraph.

                  (p) "Initial Purchasers" shall have the meaning indicated in
         the introductory paragraph.

                  (q) "Issuer" shall have the meaning indicated in the
         introductory paragraph.

                  (r) "Material Event" shall have the meaning indicated in
         Section 3(b)(vi).

                  (s) "Notes" shall have the meaning indicated in the
         introductory paragraph.



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                  (t) "Notice and Questionnaire" shall mean a written notice
         delivered to the Issuer containing substantially the information called
         for by the Selling Security Holder Notice and Questionnaire attached as
         Annex A to the Offering Memorandum.

                  (u) "Notice Holder" shall mean, on any date, any Holder that
         has delivered a Notice and Questionnaire to the Issuer on or prior to
         such date.

                  (v) "Offering Memorandum" shall mean the offering memorandum,
         dated January 31, 2001, as amended or supplemented, of the Issuer
         relating to the Notes including any and all annexes thereto and any
         information incorporated by reference therein.

                  (w) "Participant" shall have the meaning indicated in Section
         7(a).

                  (x) "Person" shall mean a corporation, limited liability
         company, association, partnership (whether general or limited),
         organization, business, individual, government or political subdivision
         thereof or governmental agency.

                  (y) "Prospectus" shall mean the prospectus included in any
         Shelf Registration, as amended or supplemented by any amendment or
         prospectus supplement, including post-effective amendments, and all
         materials incorporated by reference or explicitly deemed to be
         incorporated by reference in such Prospectus.

                  (z) "Purchase Agreement" shall have the meaning indicated in
         the introductory paragraph.

                  (aa) "Registrable Securities" shall mean the Securities until
         such time as: (i) in the circumstances contemplated by Section 2(a), a
         registration statement registering such Securities under the Securities
         Act has been declared or becomes effective and such Securities have
         been sold or otherwise transferred by the Holder thereof pursuant to
         such effective registration statement; (ii) such Securities are sold
         pursuant to Rule 144 under circumstances in which any legend borne by
         such Securities relating to restrictions on transferability thereof,
         under the Securities Act or otherwise, is removed or such Securities
         are eligible to be sold pursuant to paragraph (k) of Rule 144; or (iii)
         such Securities shall cease to be outstanding.

                  (bb) "Registration Default" shall have the meaning indicated
         in Section 2(c).

                  (cc) "Registration Default Damages" shall have the meaning
         indicated in Section 2(c).

                  (dd) "Registration Expenses" shall have the meaning indicated
         in Section 5.

                  (ee) "Resale Period" shall mean the period beginning on the
         date the Shelf Registration becomes effective and ending on the
         Termination Date.

                  (ff) "Restricted Holder" shall mean (i) a Holder that is an
         affiliate of the Issuer within the meaning of Rule 405 or (ii) a
         broker-dealer who receives Securities for its own



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         account but did not acquire the Securities as a result of market-making
         activities or other trading activities.

                  (gg) "Rule 144," "Rule 144(k)," "Rule 405" and "Rule 415"
         shall mean, in each case, such rule promulgated under the Securities
         Act.

                  (hh) "Securities" shall mean, collectively, the Notes and the
         Shares.

                  (ii) "Securities Act" shall mean the Securities Act of 1933,
         as amended, and the rules and regulations of the Commission promulgated
         thereunder.

                  (jj) "Shares" shall mean the shares of Common Stock into which
         the Notes are convertible or that have been issued upon any conversion
         from Notes into Common Stock.

                  (kk) "Shelf Registration" shall have the meaning indicated in
         Section 2(a)

                  (ll) "Termination Date" shall have the meaning indicated in
         Section 2(a).

                  (mm) "Trustee" shall have the meaning indicated in the
         introductory paragraph.

                  (nn) "Trust Indenture Act" shall mean the Trust Indenture Act
         of 1939, as amended and the rules and regulations of the Commission
         promulgated thereunder.

         Unless the context otherwise requires, any reference herein to a
"Section" or "clause" refers to a Section or clause, as the case may be, of this
Agreement, and the words "herein," "hereof" and "hereunder" and other words of
similar import refer to this Agreement as a whole and not to any particular
Section or other subdivision. Unless the context otherwise requires, any
reference to a statute, act, rule or regulation refers to the same (including
any successor statute, act, rule or regulation thereto) as it may be amended
from time to time.

         2. Registration Under the Securities Act.

                  (a) The Issuer agrees to use commercially reasonable efforts
         to file with the Commission under the Securities Act as promptly as
         practicable but in any event on or prior to the 120th day after the
         Closing Date one or more "shelf" registration statements (collectively,
         the "Shelf Registration") on an appropriate form providing for the
         registration of, and the sale on a continuous or delayed basis by the
         Holders of, all of the Registrable Securities, pursuant to Rule 415
         under the Securities Act. The Issuer agrees to use commercially
         reasonable efforts to cause the Shelf Registration to become or be
         declared effective under the Securities Act no later than 180 days
         after the Closing Date and to keep such Shelf Registration continuously
         effective for a period ending on the earliest of (i) the time when all
         the Securities registered under the Shelf Registration can be sold by
         Persons who are not affiliates of the Issuer pursuant to Rule 144(k),
         (ii) the second anniversary of the Closing Date, (iii) the date on
         which all Securities registered under the Shelf Registration are
         disposed of in accordance therewith, and (iv) the date upon which there
         are no longer any Registrable Securities outstanding (the earliest date
         on which any such event occurs being the "Termination Date"). The
         Issuer agrees to give



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         notice to the Holders of all of the Registrable Securities of the
         filing and effectiveness of the Shelf Registration. The Issuer further
         agrees to supplement or make amendments to the Shelf Registration, as
         and when required by the rules, regulations or instructions applicable
         to the registration form used for such Shelf Registration or by the
         Securities Act and the Issuer agrees to furnish to the Notice Holders
         of the Registrable Securities copies of any such supplement or
         amendment prior to its being used or promptly following its filing with
         the Commission.

                  (b) Each Holder of Registrable Securities agrees that if such
         Holder wishes to sell Registrable Securities pursuant to a Shelf
         Registration and related Prospectus, it will do so only in accordance
         with this Section 2(b) and Section 3(g). Each Holder of Registrable
         Securities wishing to sell Registrable Securities pursuant to a Shelf
         Registration and related Prospectus agrees to deliver a Notice and
         Questionnaire to the Issuer at least three (3) Business Days prior to
         any intended distribution of Registrable Securities under the Shelf
         Registration. From and after the Effective Time, the Issuer shall, as
         promptly as is practicable after the date a Notice and Questionnaire is
         delivered, and in any event within five (5) Business Days after such
         date, (i) if required by applicable law, file with the Commission a
         post-effective amendment to the Shelf Registration or prepare and, if
         required by applicable law, file a supplement to the related Prospectus
         or a supplement or amendment to any document incorporated therein by
         reference or file any other required document so that such Notice
         Holder is named as a selling security Holder in the Shelf Registration
         and the related Prospectus and so that such Notice Holder is permitted
         to deliver such Prospectus to purchasers of the Registrable Securities
         in accordance with applicable law and, if the Issuer shall file a
         post-effective amendment to the Shelf Registration, use commercially
         reasonable efforts to cause such post-effective amendment to be
         declared effective under the Securities Act as promptly as is
         practicable; (ii) provide such Holder copies of any documents filed
         pursuant to Section 2(b)(i); and (iii) notify such Holder as promptly
         as practicable after the effectiveness under the Securities Act of any
         post-effective amendment filed pursuant to Section 2(b)(i); provided,
         that if such Notice and Questionnaire is delivered during a Deferral
         Period, the Issuer shall so inform the Notice Holder and shall take the
         actions set forth in clauses (i), (ii) and (iii) above upon expiration
         of the Deferral Period in accordance with Section 3(g). Notwithstanding
         anything contained herein to the contrary, the Issuer shall be under no
         obligation to name any Holder that is not a Notice Holder as a selling
         security Holder in any Shelf Registration or related Prospectus;
         provided, however, that any Holder that becomes a Notice Holder
         pursuant to the provisions of Section 2(b) (whether or not such Holder
         was a Notice Holder at the time the Shelf Registration was declared
         effective) shall be named as a selling security Holder in the Shelf
         Registration or related Prospectus in accordance with the requirements
         of this Section 2(b).

                  (c) If any of the following events (any such event a
         "Registration Default") shall occur, then the Issuer shall pay
         liquidated damages (the "Registration Default Damages") to the Holders
         in respect of the Registrable Securities as follows:

                           (i) if the Shelf Registration is not filed with the
                  Commission on or prior to the 120th day following the Closing
                  Date, then commencing on the 121st



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                  day after the Closing Date, Registration Default Damages shall
                  accrue on the Applicable Principal Amount of any outstanding
                  Notes that are Registrable Securities and the Applicable
                  Conversion Price of any outstanding Shares that are
                  Registrable Securities at a rate of 0.25% per annum for the
                  first 120 days from and including such 121st day and 0.5% per
                  annum thereafter; or

                           (ii) if the Shelf Registration is filed but not
                  declared effective by the Commission on or prior to the 180th
                  day following the Closing Date, then commencing on the 181st
                  day after the Closing Date, Registration Default Damages shall
                  accrue on the Applicable Principal Amount of any outstanding
                  Notes that are Registrable Securities and the Applicable
                  Conversion Price of any outstanding Shares that are
                  Registrable Securities at a rate of 0.25% per annum for the
                  first 120 days from and including such 181st day and 0.5% per
                  annum thereafter; or

                           (iii) if the Shelf Registration has been declared
                  effective but such Shelf Registration ceases to be effective
                  (other than pursuant to Section 3(g) hereof) at any time prior
                  to the Termination Date, then commencing on the day such Shelf
                  Registration ceases to be effective, Registration Default
                  Damages shall accrue on the Applicable Principal Amount of any
                  outstanding Notes that are Registrable Securities and the
                  Applicable Conversion Price of any outstanding Shares that are
                  Registrable Securities at a rate of 0.25% per annum for the
                  first 120 days from and including such date on which the Shelf
                  Registration ceases to be effective and 0.5% per annum
                  thereafter; or

                           (iv) if the aggregate duration of Deferral Periods in
                  any period exceeds the number of days permitted in respect of
                  such period pursuant to Section 3(g) hereof, then commencing
                  on the day the aggregate duration of Deferral Periods in any
                  period exceeds the number of days permitted in respect of such
                  period, Registration Default Damages shall accrue on the
                  Applicable Principal Amount of any outstanding Notes that are
                  Registrable Securities and the Applicable Conversion Price of
                  any outstanding Shares that are Registrable Securities at a
                  rate of 0.25% per annum for the first 120 days from and
                  including such date and 0.5% per annum thereafter;

         provided, however, that (1) upon the filing of the Shelf Registration
         (in the case of clause (i) above), (2) upon the effectiveness of the
         Shelf Registration (in the case of clause (ii) above), (3) upon the
         effectiveness of the Shelf Registration which had ceased to remain
         effective (in the case of clause (iii) above), (4) upon the termination
         of the Deferral Period that caused the limit on the aggregate duration
         of Deferral Periods in a period set forth in Section 3(g) to be
         exceeded (in the case of clause (iv) above) or (5) upon the Termination
         Date, Registration Default Damages on all Securities shall cease to
         accrue. It is understood and agreed that, notwithstanding any provision
         to the contrary, so long as any Registrable Security is then capable of
         being sold under an effective Shelf Registration Statement, no
         Registration Default Damages shall accrue on such Registrable Security.
         Registration Default Damages shall constitute the sole monetary damages
         with respect to any matters covered in this Section 2(c).



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                  (d) Any reference herein to a registration statement shall be
         deemed to include any document incorporated therein by reference as of
         the applicable Effective Time and any reference herein to any
         post-effective amendment to a registration statement shall be deemed to
         include any document incorporated therein by reference as of a time
         after such Effective Time.

                  (e) Notwithstanding any other provision of this Agreement, any
         Holder of Registrable Securities who does not comply with the
         provisions of Section 3(d), if applicable, shall not be entitled to
         receive Registration Default Damages unless and until such Holder
         complies with the provisions of Section 3(d), as applicable.

                  (f) Any amounts of Registration Default Damages due pursuant
         to Section 2(c) will be payable in cash semi-annually on each February
         7 and August 7 (each a "Damages Payment Date"), commencing with the
         first such date occurring after any such Registration Default Damages
         commences to accrue, to Holders of record on the January 23 or July 23
         next preceding such Damages Payment Date with respect to Notes that are
         Registrable Securities or with respect to outstanding Shares that are
         Registrable Securities. The amount of Registration Default Damages for
         Registrable Securities will be determined on the basis of a 360-day
         year comprised of twelve 30-day months.

         3. Registration Procedures. The following provisions shall apply to
registration statements filed pursuant to Section 2:

                  (a) At the Effective Time of the Shelf Registration, the
         Issuer shall qualify the Indenture under the Trust Indenture Act.

                  (b) The Issuer shall, with respect to any such registration
         statement:

                           (i) prepare and file with the Commission a
                  registration statement with respect to the Shelf Registration
                  on any form which may be utilized by the Issuer and which
                  shall permit the disposition of the Registrable Securities in
                  accordance with the intended method or methods thereof, as
                  specified in writing by the Holders of the Registrable
                  Securities, and use commercially reasonable efforts to cause
                  such registration statement to become effective in accordance
                  with Section 2(a) above;

                           (ii) prepare and file with the Commission such
                  amendments and supplements to such registration statement and
                  the Prospectus included therein as may be necessary to effect
                  and maintain the effectiveness of such registration statement
                  for the period specified in Section 2(a), and as may be
                  required by the applicable rules and regulations of the
                  Commission and the instructions applicable to the form of such
                  registration statement and as may be necessary to permit the
                  Holders of the Registrable Securities to deliver the
                  Prospectus to purchasers of such Securities, and furnish to
                  the Notice Holders of the Registrable Securities copies of any
                  such supplement or amendment simultaneously with or prior to
                  its being used or filed with the Commission;



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                           (iii) comply, as to all matters within the Issuer's
                  control, with the provisions of the Securities Act with
                  respect to the disposition of all of the Registrable
                  Securities covered by such registration statement in
                  accordance with the intended methods of disposition by the
                  Holders thereof provided for in such registration statement;

                           (iv) provide to any of (A) the Notice Holders, (B)
                  the underwriters (which term, for purposes of this Agreement,
                  shall include a Person deemed to be an underwriter within the
                  meaning of Section 2(11) of the Securities Act), if any,
                  thereof, (C) the sales or placement agent, if any, therefor,
                  (D) counsel for such underwriters or agent and (E) not more
                  than one counsel for all the Holders of such Registrable
                  Securities who so request of the Issuer in writing the
                  opportunity to participate in the preparation of such
                  registration statement, each Prospectus included therein or
                  filed with the Commission and each amendment or supplement
                  thereto;

                           (v) for a reasonable period prior to the filing of
                  such registration statement, and throughout the Resale Period,
                  make available at reasonable times at the Issuer's principal
                  place of business or such other reasonable place for
                  inspection by the Persons referred to in Section 3(b)(iv), who
                  shall certify to the Issuer that they have or are acting on
                  behalf of a Holder who has a current intention to sell
                  Registrable Securities pursuant to the Shelf Registration,
                  such financial and other information and books and records of
                  the Issuer, and cause the officers, employees, counsel and
                  independent certified public accountants of the Issuer to
                  respond to such inquiries, as shall be reasonably necessary,
                  in the judgment of the respective counsel referred to in such
                  Section, to conduct a reasonable investigation within the
                  meaning of Section 11 of the Securities Act; provided,
                  however, that each such party shall be required to maintain in
                  confidence and not to disclose to any other Person or
                  otherwise use or take advantage of any information or records
                  reasonably designated by the Issuer in writing as being
                  confidential, until such time as (A) such information becomes
                  a matter of public record (whether by virtue of its inclusion
                  in such registration statement or otherwise), (B) such Person
                  shall be required so to disclose such information pursuant to
                  a subpoena or order of any court or other governmental agency
                  or body having jurisdiction over the matter (subject to the
                  requirements of such order, and only after such Person shall
                  have given the Issuer prompt prior written notice of such
                  requirement and the opportunity to contest the same or seek an
                  appropriate protective order), or (C) subject to Section 3(g),
                  such information is required to be set forth in such
                  registration statement or the Prospectus included therein or
                  in an amendment to such registration statement or an amendment
                  or supplement to such Prospectus in order that such
                  registration statement, Prospectus, amendment or supplement,
                  as the case may be, does not contain an untrue statement of a
                  material fact or omit to state therein a material fact
                  required to be stated therein or necessary to make the
                  statements therein not misleading, and the Issuer may require
                  each such Person to execute a written agreement to comply with
                  the above confidentiality requirements;



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                           (vi) promptly notify Holders of Registrable
                  Securities included in such registration statement, the sales
                  or placement agent, if any, therefor and the managing
                  underwriter or underwriters, if any, thereof named in the
                  Shelf Registration or a supplement thereto, and confirm such
                  notice in writing, (A) when such registration statement or the
                  Prospectus included therein or any Prospectus amendment or
                  supplement or post-effective amendment has been filed, and,
                  with respect to such registration statement or any
                  post-effective amendment, when the same has become effective,
                  (B) of the issuance by the Commission of any stop order
                  suspending the effectiveness of such registration statement or
                  the initiation or written threat of any proceedings for that
                  purpose, (C) of the receipt by the Issuer of any notification
                  with respect to the suspension of the qualification of the
                  Registrable Securities for sale in any jurisdiction or the
                  initiation or written threat of any proceeding for such
                  purpose, (D) of the occurrence of (but not the nature of or
                  details concerning) any event or the existence of any fact (a
                  "Material Event") as a result of which any Shelf Registration
                  shall contain any untrue statement of a material fact or omit
                  to state any material fact required to be stated therein or
                  necessary to make the statements therein not misleading, or
                  any Prospectus shall contain any untrue statement of a
                  material fact or omit to state any material fact required to
                  be stated therein or necessary to make the statements therein,
                  in the light of the circumstances under which they were made,
                  not misleading, (E) of the determination by the Issuer that a
                  post-effective amendment to a Shelf Registration will be filed
                  with the Commission, which notice may, at the discretion of
                  the Issuer (or as required pursuant to Section 3(g)), state
                  that it constitutes a Deferral Notice, in which event the
                  provisions of Section 3(g) shall apply or (F) at any time when
                  a Prospectus is required to be delivered under the Securities
                  Act, that such registration statement, Prospectus, Prospectus
                  amendment or supplement or post-effective amendment does not
                  conform in all material respects to the applicable
                  requirements of the Securities Act and the Trust Indenture
                  Act;

                           (vii) use commercially reasonable efforts to obtain
                  the withdrawal of any order suspending the effectiveness of
                  such registration statement or any post-effective amendment
                  thereto at the earliest practicable date;

                           (viii) if requested by any managing underwriter or
                  underwriters, any placement or sales agent or any Holder of
                  Registrable Securities included in the Shelf Registration,
                  promptly incorporate in a Prospectus supplement or
                  post-effective amendment such information as is required by
                  the applicable rules and regulations of the Commission
                  relating to the terms of the sale of such Registrable
                  Securities, including information with respect to the
                  principal amount at maturity or number of Registrable
                  Securities being sold by such Holder or agent or to any
                  underwriters, the name and description of such Holder, agent
                  or underwriter, the offering price of such Registrable
                  Securities and any discount, commission or other compensation
                  payable in respect thereof, the purchase price being paid
                  therefor by such underwriters and with respect to any other
                  terms of the offering of the Registrable Securities to be sold
                  by such Holder or agent or to such underwriters; and make all
                  required filings of such Prospectus supplement or



                                      -11-
<PAGE>   12



                  post-effective amendment promptly after notification of the
                  matters to be incorporated in such Prospectus supplement or
                  post-effective amendment;

                           (ix) furnish to each Holder of Registrable Securities
                  included in the Shelf Registration, each placement or sales
                  agent, if any, therefor, each underwriter, if any, thereof and
                  the respective counsel referred to in Section 3(b)(iv) one
                  conformed copy of such registration statement and each such
                  amendment or supplement thereto (in each case including all
                  exhibits thereto) and such number of copies of the Prospectus
                  included in such registration statement (including each
                  preliminary Prospectus and any summary Prospectus) as such
                  Person shall reasonably request, in each case in conformity in
                  all material respects with the applicable requirements of the
                  Securities Act and the Trust Indenture Act; and the Issuer
                  hereby consents (except during such periods that a Deferral
                  Notice is outstanding and has not been revoked) to the use of
                  such Prospectus (including any such preliminary or summary
                  Prospectus) and any amendment or supplement thereto by each
                  such Holder and by any such agent and underwriter, in each
                  case in the form most recently provided to such Person by the
                  Issuer in connection with the offering and sale of the
                  Registrable Securities covered by the Prospectus (including
                  any such preliminary or summary Prospectus) or any supplement
                  or amendment thereto; and

                           (x) use its commercially reasonable efforts to (A)
                  register or qualify, to the extent required by law, the
                  Registrable Securities to be included in such registration
                  statement under such securities laws or blue sky laws of such
                  United States jurisdictions as any Holder of such Registrable
                  Securities included in the Shelf Registration and each
                  placement or sales agent, if any, therefor and underwriter, if
                  any, thereof shall reasonably request, and (B) keep such
                  registrations or qualifications in effect and comply with such
                  laws so as to permit the continuance of offers, sales and
                  dealings therein in such jurisdictions during the period the
                  Shelf Registration is required to remain effective under
                  Section 2(a) and for so long as may be necessary to enable any
                  such Holder, agent or underwriter to complete its distribution
                  of Securities pursuant to such registration statement but in
                  any event not later than the date through which the Issuer is
                  required to keep the Shelf Registration effective pursuant to
                  Section 2(a); provided, however, that the Issuer shall not be
                  required for any such purpose to (1) qualify as a foreign
                  corporation in any jurisdiction wherein it would not otherwise
                  be required to qualify but for the requirements of this
                  Section 3(b)(x), (2) consent to general service of process in
                  any such jurisdiction, or (3) make any changes to its
                  certificate of incorporation or by-laws or any agreement
                  between it and its stockholders.

         In case any of the foregoing obligations is dependent upon information
         provided or to be provided by a party other than the Issuer, such
         obligation shall be subject to the provision of such information by
         such party; provided that the Issuer shall use commercially reasonable
         efforts to obtain the necessary information from any party responsible
         for providing such information.



                                      -12-
<PAGE>   13




                  (c) Each Holder of Registrable Securities agrees that upon
         receipt of any notice from the Issuer, pursuant to Section 3(b)(vi)(D),
         such Holder shall forthwith discontinue (and cause any placement or
         sales agent or underwriters acting on their behalf to discontinue) the
         disposition of Registrable Securities pursuant to the registration
         statement applicable to such Registrable Securities until such Holder
         (i) shall have received copies of such amended or supplemented
         Prospectus and, if so directed by the Issuer, such Holder shall deliver
         to the Issuer (at the Issuer's expense) all copies, other than
         permanent file copies, then in such Holder's possession of the
         Prospectus covering such Registrable Securities at the time of receipt
         of such notice or (ii) shall have received notice from the Issuer that
         the disposition of Registrable Securities pursuant to the Shelf
         Registration may continue.

                  (d) The Issuer may require each Holder of Registrable
         Securities as to which any registration pursuant to Section 2(a) is
         being effected to furnish to the Issuer such information regarding such
         Holder and such Holder's intended method of distribution of such
         Registrable Securities as the Issuer may from time to time reasonably
         request in writing, but only to the extent that such information is
         required in order to comply with the Securities Act or other applicable
         federal or state securities or blue sky laws. Each such Holder agrees
         to notify the Issuer as promptly as practicable of any inaccuracy or
         change in information previously furnished by such Holder to the Issuer
         or of the occurrence of any event in either case as a result of which
         any Prospectus relating to such registration contains or would contain
         an untrue statement of a material fact regarding such Holder or such
         Holder's intended method of disposition of such Registrable Securities
         or omits to state any material fact regarding such Holder or such
         Holder's intended method of disposition of such Registrable Securities
         required to be stated therein or necessary to make the statements
         therein not misleading, and promptly to furnish to the Issuer any
         additional information required to correct and update any previously
         furnished information or required so that such Prospectus shall not
         contain, with respect to such Holder or the disposition of such
         Registrable Securities, an untrue statement of a material fact or omit
         to state a material fact required to be stated therein or necessary to
         make the statements therein not misleading.

                  (e) Until the expiration of two years after the Closing Date,
         the Issuer will not, and will not permit any of its "affiliates" (as
         defined in Rule 144) to, resell any of the Notes that have been
         reacquired by any of them except pursuant to an effective registration
         statement under the Securities Act.

                  (f) Subject to Section 3(g), upon the occurrence of a Material
         Event, the Issuer shall as promptly as practicable prepare and file a
         post-effective amendment to the Shelf Registration or a supplement to
         the related Prospectus or any document incorporated therein by
         reference or file any other required document that would be
         incorporated by reference into such Shelf Registration and Prospectus
         so that such Shelf Registration does not contain any untrue statement
         of a material fact or omit to state any material fact required to be
         stated therein or necessary to make the statements therein not
         misleading, and such Prospectus does not contain any untrue statement
         of a material fact or omit to state any material fact required to be
         stated therein or necessary to make the statements therein, in the
         light of the circumstances under which they were made, not



                                      -13-
<PAGE>   14



         misleading, as thereafter delivered to the purchasers of the
         Registrable Securities being sold thereunder, and, in the case of a
         post-effective amendment to a Shelf Registration, use commercially
         reasonable efforts to cause it to be declared effective as promptly as
         is reasonably practicable. The Issuer shall prepare and furnish to each
         such Holder, to each placement or sales agent, if any, and to each such
         underwriter, if any, a reasonable number of copies of any such
         Prospectus supplemented or amended so that, as thereafter delivered to
         purchasers of Registrable Securities, such Prospectus shall conform in
         all material respects to the applicable requirements of the Securities
         Act and the Trust Indenture Act.

                  (g) Upon the occurrence or existence of any pending corporate
         development or any other Material Event that, in the sole judgment of
         the Issuer, makes it appropriate to suspend the availability of the
         Shelf Registration and the related Prospectus, the Issuer shall give
         notice (without notice of the nature or details of such events) to the
         Notice Holders that the availability of the Shelf Registration is
         suspended (a "Deferral Notice") and, upon receipt of any Deferral
         Notice, each Notice Holder agrees not to sell any Registrable
         Securities pursuant to the Shelf Registration until such Notice
         Holder's receipt of copies of the supplemented or amended Prospectus
         provided for in clause (f) above, or until it is advised in writing by
         the Issuer that the Prospectus may be used, and has received copies of
         any additional or supplemental filings that are incorporated or deemed
         incorporated by reference in such Prospectus. The period during which
         the availability of the Shelf Registration and any Prospectus is
         suspended (the "Deferral Period") shall, without the Issuer incurring
         any obligation to pay Registration Default Damages pursuant to Section
         2(c), not exceed sixty (60) days in any three (3) month period or
         ninety (90) days in any twelve (12) month period. The Issuer's
         obligations under Sections 3(b) and 3(f) shall be suspended during any
         Deferral Period.

         4. Holder's Obligations. Each Holder agrees, by acquisition of the
Registrable Securities, that no Holder of Registrable Securities shall be
entitled to sell any of such Registrable Securities pursuant to a Shelf
Registration or to receive a Prospectus relating thereto, unless such Holder has
furnished the Issuer with a Notice and Questionnaire as required pursuant to
Section 2(b) hereof (including the information required to be included in such
Notice and Questionnaire) and the information set forth in the next sentence.
Each Notice Holder agrees promptly to furnish to the Issuer all information
required to be disclosed in order to make the information previously furnished
to the Issuer by such Notice Holder not misleading and any other information
regarding such Notice Holder and the distribution of such Registrable Securities
as may be required to be disclosed in the Shelf Registration under applicable
law or pursuant to SEC comments. Each Holder further agrees not to sell any
Registrable Securities pursuant to the Shelf Registration without delivering, or
causing to be delivered, a Prospectus to the purchaser thereof and, following
the Termination Date, to notify the Issuer, within 10 business days of request,
of the amount of Registrable Securities sold pursuant to the Shelf Registration
and, in the absence of a response, the Issuer may assume that all of the
Holder's Registrable Securities were so sold. Each Holder specifically agrees
that no underwritten offerings of Registrable Securities may be effected without
the Issuer's prior agreement.

         5. Registration Expenses. The Issuer agrees to bear and to pay or cause
to be paid promptly upon request being made therefor all expenses incident to
the Issuer's performance of



                                      -14-
<PAGE>   15



or compliance with this Agreement, including (a) all Commission and any NASD
registration and filing fees and expenses, (b) all fees and expenses in
connection with the qualification of the Securities for offering and sale under
the state securities and blue sky laws referred to in Section 3(b)(x) hereof,
including reasonable fees and disbursements of one counsel (selected as set
forth in clause (j) below) for the placement or sales agent or underwriters, if
any, in connection with such qualifications, (c) all expenses relating to the
preparation, printing, distribution and reproduction of each registration
statement required to be filed hereunder, each Prospectus included therein or
prepared for distribution pursuant hereto, each amendment or supplement to the
foregoing, the certificates representing the Securities and all other documents
relating hereto, (d) all costs and expenses relating to qualifying the
Securities with The Depository Trust Company and to admitting the Securities for
trading in the PORTAL market, (e) fees and expenses of the Trustee under the
Indenture, and of any paying agent, escrow agent or custodian, and of the
registrar and transfer agent for the Shares issued upon conversion of the Notes,
as well as the reasonable fees and expenses of counsel therefor, (f) internal
expenses (including all salaries and expenses of the Issuer's officers and
employees performing legal or accounting duties), (g) fees, disbursements and
expenses of counsel and independent certified public accountants of the Issuer
(including the expenses of any opinions or "cold comfort" letters required by or
incident to such performance and compliance), (h) fees and expenses of listing
the Shares on all exchanges where the Common Stock is listed, (i) fees charged
by rating agencies to rate the Notes, and (j) reasonable fees, disbursements and
expenses of one counsel for the Holders of Registrable Securities retained in
connection with the Shelf Registration (which shall initially be Bracewell &
Patterson, L.L.P., but which may, with the written consent of the Initial
Purchasers, be another nationally recognized law firm experienced in securities
matters designated by the Issuer (unless reasonably objected to by Holders of at
least a majority in aggregate Applicable Principal Amount and Applicable
Conversion Price of the Registrable Securities being registered)), and fees,
expenses and disbursements of any other Persons, including special experts,
retained by the Issuer in connection with such registration (collectively, the
"Registration Expenses"). To the extent that any Registration Expenses are
incurred, assumed or paid by any Holder of Registrable Securities or any
placement or sales agent therefor or underwriter hereof, the Issuer shall
reimburse such Person for the full amount of the Registration Expenses so
incurred, assumed or paid promptly after receipt of a documented request
therefor. Notwithstanding the foregoing, the Holders of the Registrable
Securities being registered shall pay all agency fees and commissions and
underwriting discounts and commissions attributable to the sale of such
Registrable Securities and the fees and disbursements of any counsel or other
advisors or experts retained by such Holders (severally or jointly), other than
the counsel and experts specifically referred to above.

         6. Representations and Warranties. The Issuer represents and warrants
to, and agrees with, the Initial Purchasers and each of the Holders from time to
time of Registrable Securities that:

                  (a) Each registration statement covering Registrable
         Securities and each Prospectus (including any preliminary or summary
         Prospectus) contained therein or furnished pursuant to Section 3(c)
         hereof and any further amendments or supplements to any such
         registration statement or Prospectus, when it becomes effective or is
         filed with the Commission, as the case may be, and, in the case of an
         underwritten offering of Registrable Securities, at the time of the
         closing under the underwriting agreement



                                      -15-
<PAGE>   16



         relating thereto, will conform in all material respects to the
         applicable requirements of the Securities Act and the Trust Indenture
         Act and will not contain an untrue statement of a material fact or omit
         to state a material fact required to be stated therein or necessary to
         make the statements therein not misleading; and at all times subsequent
         to the Effective Time when a Prospectus would be required to be
         delivered under the Securities Act, other than from (i) such time as a
         notice has been given to Holders of Registrable Securities pursuant to
         Section 3(b)(vi)(D) or Section 3(g) hereof until (ii) such time as the
         Issuer furnishes an amended or supplemented Prospectus pursuant to
         Section 3(f) hereof or such time as the Issuer provides notice that
         offers and sales pursuant to the Shelf Registration may continue, the
         Shelf Registration, and each Prospectus (including any summary
         Prospectus) contained therein or furnished pursuant to Section 3(b)
         hereof, as then amended or supplemented, will conform in all material
         respects to the applicable requirements of the Securities Act and the
         Trust Indenture Act; provided, however, that this representation and
         warranty shall not apply to any statements or omissions made in
         reliance upon and in conformity with information furnished in writing
         to the Issuer by or on behalf of a Holder of Registrable Securities
         expressly for use therein.

                  (b) Any documents incorporated by reference in any Prospectus
         referred to in Section 6(a) hereof, when they become or became
         effective or are or were filed with the Commission, as the case may be,
         will conform or conformed in all material respects to the requirements
         of the Securities Act or the Exchange Act, as applicable, and none of
         such documents will contain or contained an untrue statement of a
         material fact or will omit or omitted to state a material fact required
         to be stated therein or necessary to make the statements therein not
         misleading, provided, however, that this representation and warranty
         shall not apply to any statements or omissions made in reliance upon
         and in conformity with information furnished in writing to the Issuer
         by a Holder of Registrable Securities expressly for use therein.

                  (c) The compliance by the Issuer with all of the provisions of
         this Agreement and the consummation of the transactions herein
         contemplated will not contravene any provision of applicable law or the
         certificate of incorporation or by-laws of the Issuer or, except to the
         extent that any such contravention would not have a material adverse
         effect on the Issuer and its subsidiaries, taken as a whole, any
         indenture or instrument relating to indebtedness for money borrowed or
         any agreement to which the Issuer is a party or any order, rule,
         regulation or decree of any court or governmental agency or authority
         located in the United States having jurisdiction over the Issuer or any
         property of the Issuer; and, to the best knowledge of the Issuer, no
         consent, authorization or order of, or filing or registration with, any
         court or governmental agency or authority is required for the
         consummation by the Issuer of the transactions contemplated by this
         Agreement, except the registration under the Securities Act
         contemplated hereby, qualification of the Indenture under the Trust
         Indenture Act and such consents, approvals, authorizations,
         registrations or qualifications as may be required under State
         securities or blue sky laws.

                  (d) This Agreement has been duly authorized, executed and
         delivered by the Issuer.


                                      -16-
<PAGE>   17

         7. Indemnification.

                  (a) Indemnification by the Issuer. In connection with the
         Shelf Registration, the Issuer shall, and hereby agrees to, indemnify
         and hold harmless each of the Holders of Registrable Securities
         included in such Shelf Registration, and each Person who is named in
         such Shelf Registration or a supplement thereto as an underwriter in
         any offering or sale of such Registrable Securities, such Person's
         partners, principals, directors and officers and each Person who
         controls any such Person (each, a "Participant") against any losses,
         claims, damages or liabilities, joint or several, to which such
         Participant may become subject under the Securities Act, the Exchange
         Act or other federal or state statutory law or regulation, at common
         law or otherwise, insofar as such losses, claims, damages or
         liabilities (or actions in respect thereof) arise out of or are based
         upon an untrue statement or alleged untrue statement of a material fact
         contained in any registration statement under which such Registrable
         Securities were registered under the Securities Act, or any
         preliminary, final or summary Prospectus contained therein or furnished
         by the Issuer to any such Participant, or any amendment or supplement
         thereto, or arise out of or are based upon the omission or alleged
         omission to state therein a material fact required to be stated therein
         or necessary to make the statements therein not misleading and the
         Issuer shall, and hereby agrees to, reimburse each such Participant for
         any legal or other expenses reasonably incurred by it in connection
         with investigating or defending any such loss, claim, damage, liability
         or action; provided, however, that the Issuer shall not be liable to
         any such Person in any such case to the extent that any such loss,
         claim, damage or liability arises out of or is based upon an untrue
         statement or alleged untrue statement or omission or alleged omission
         made in such registration statement, or preliminary, final or summary
         Prospectus, or amendment or supplement thereto, in reliance upon and in
         conformity with written information furnished to the Issuer by such
         Participant expressly for use therein; provided, further, that this
         indemnity agreement shall not apply to any loss, liability, claim,
         damage or expense arising from (i) an offer or sale of Registrable
         Securities occurring during a Deferral Period, if Notice Holders
         received a Deferral Notice, or (ii) the Participant's failure to
         deliver at or prior to the written confirmation of sale, the most
         recent Prospectus, as amended or supplemented, and such Prospectus, as
         amended or supplemented, would have corrected such untrue statement or
         alleged untrue statement of a material fact. This indemnity agreement
         will be in addition to any liability which the Issuer may otherwise
         have.

                  (b) Indemnification by Participants. Each Participant,
         severally and not jointly, agrees to indemnify and hold harmless the
         Issuer, each of the Issuer's directors and officers and each Person who
         controls the Issuer within the meaning of either the Securities Act or
         the Exchange Act, to the same extent as the foregoing indemnity from
         the Issuer, but only with reference to written information furnished to
         the Issuer by or on behalf of such Participant specifically for use in
         any registration statement, or any preliminary or final or summary
         Prospectus contained therein or any amendment or supplement thereto.
         This indemnity agreement will be acknowledged by each Participant that
         is not an Initial Purchaser in such Participant's Notice and
         Questionnaire and will be in addition to any liability which any such
         Person may otherwise have.

                  (c) Promptly after receipt by an indemnified party under
         Section 7(a) or (b) of notice of the commencement of any action, such
         indemnified party will, if a claim in respect thereof is to be made
         against the indemnifying party under such subsection, notify



                                      -17-
<PAGE>   18



         the indemnifying party in writing of the commencement thereof; but the
         omission so to notify the indemnifying party will not relieve the
         indemnifying party from any liability which it may have to any
         indemnified party otherwise than under Section 7(a) or (b). In case any
         such action is brought against any indemnified party, and it notifies
         the indemnifying party of the commencement thereof, the indemnifying
         party will be entitled to participate therein, and to the extent that
         it may elect by written notice delivered to the indemnified party
         promptly after receiving the aforesaid notice from such indemnified
         party, to assume the defense thereof; provided that, if the defendants
         in any such action include both the indemnified party and the
         indemnifying party and representation of both parties by the same
         counsel would be inappropriate due to actual or potential conflicting
         interests between them, the indemnified party or parties shall have the
         right to select separate counsel to participate in the defense of such
         action on behalf of such indemnified party or parties. Upon receipt of
         notice from the indemnifying party to such indemnified party of its
         election so to assume the defense of such action, the indemnifying
         party will not be liable to such indemnified party under Section 7(a)
         or (b) for any legal or other expenses subsequently incurred by such
         indemnified party (other than reasonable costs of investigation) in
         connection with the defense thereof unless (i) the indemnified party
         shall have employed separate counsel in connection with the assertion
         of legal defenses in accordance with the proviso to the immediately
         preceding sentence (it being understood, however, that the indemnifying
         party shall not be liable for the expenses of more than one separate
         national counsel, approved by the indemnifying party, representing the
         indemnified parties who are parties to such action), (ii) the
         indemnifying party shall not have employed counsel satisfactory to the
         indemnified party to represent the indemnified party within a
         reasonable time after notice of commencement of the action or (iii) the
         indemnifying party has authorized the employment of counsel for the
         indemnified party at the expense of the indemnifying party; and except
         that, if clause (i) or (iii) is applicable, such liability shall be
         only in respect of the counsel referred to in such clause (i) or (iii).

         No indemnifying party shall, without the prior written consent of the
         indemnified party, effect any settlement of any pending or threatened
         action in respect of which any indemnified party is or could have been
         a party and indemnity could have been sought hereunder by such
         indemnified party unless such settlement includes an unconditional
         release of such indemnified party from all liability on any claims that
         are the subject matter of such action. No indemnifying party shall be
         liable for any settlement effected without its consent.

                  (d) Contribution. Each party hereto agrees that, if for any
         reason the indemnification provisions contemplated by Section 7(a) or
         Section 7(b) are unavailable to or insufficient to hold harmless an
         indemnified party in respect of any losses, claims, damages or
         liabilities (or actions in respect thereof) referred to therein, then
         each indemnifying party shall contribute to the amount paid or payable
         by such indemnified party as a result of such losses, claims, damages
         or liabilities (or actions in respect thereof) in such proportion as is
         appropriate to reflect the relative fault of the indemnifying party and
         the indemnified party in connection with the statements or omissions
         which resulted in such losses, claims, damages or liabilities (or
         actions in respect thereof), as well as any other relevant equitable
         considerations. The relative fault



                                      -18-
<PAGE>   19



         of such indemnifying party and indemnified party shall be determined by
         reference to, among other things, whether the untrue or alleged untrue
         statement of a material fact or omission or alleged omission to state a
         material fact relates to information supplied by such indemnifying
         party or by such indemnified party, and the parties' relative intent,
         knowledge, access to information and opportunity to correct or prevent
         such statement or omission. The parties hereto agree that it would not
         be just and equitable if contributions pursuant to this Section 7(d)
         were determined by pro rata allocation (even if the Participants were
         treated as one entity for such purpose) or by any other method of
         allocation which does not take account of the equitable considerations
         referred to in this Section 7(d). The amount paid or payable by an
         indemnified party as a result of the losses, claims, damages, or
         liabilities (or actions in respect thereof) referred to above shall be
         deemed to include any legal or other fees or expenses reasonably
         incurred by such indemnified party in connection with investigating or
         defending any such action or claim. Notwithstanding the provisions of
         this Section 7(d), no Participant shall be required to contribute any
         amount in excess of the amount by which the dollar amount of the
         proceeds received by such Participant from the sale of any Registrable
         Securities exceeds the amount of any damages which such Participant has
         otherwise been required to pay by reason of such untrue or alleged
         untrue statement or omission or alleged omission, and no underwriter
         shall be required to contribute any amount in excess of the amount by
         which the total price at which the Registrable Securities underwritten
         by it and distributed to the public were offered to the public exceeds
         the amount of any damages which such underwriter has otherwise been
         required to pay by reason of such untrue or alleged untrue statement or
         omission or alleged omission. No Person guilty of fraudulent
         misrepresentation (within the meaning of Section 11(f) of the
         Securities Act) shall be entitled to contribution from any Person who
         was not guilty of such fraudulent misrepresentation. The Participants'
         obligations in this Section 7(d) to contribute shall be several in
         proportion to the aggregate principal amount at maturity or number of
         Registrable Securities registered or underwritten, as the case may be,
         by them and not joint.

                  (e) The obligations of the Issuer under this Section 7 shall
         be, in addition to any liability which the Issuer may otherwise have
         and shall extend, upon the same terms and conditions, to each officer,
         director, principal and partner of each Participant and each Person, if
         any, who controls any Participant within the meaning of the Securities
         Act or the Exchange Act; and the obligations of the Participants
         contemplated by this Section 7 shall be in addition to any liability
         which the respective Participants may otherwise have and shall extend,
         upon the same terms and conditions, to each officer and director of the
         Issuer (including any Person who, with such Person's consent, is named
         in any registration statement as about to become a director of the
         Issuer), and to each Person, if any, who controls the Issuer within the
         meaning of the Securities Act or the Exchange Act.

         8. Rule 144. The Issuer covenants to the Holders of Registrable
Securities that, until the Termination Date, the Issuer shall use commercially
reasonable efforts to timely file the reports required to be filed by it under
the Exchange Act referred to in subparagraph (c)(1) of Rule 144 adopted by the
Commission under the Securities Act. Upon the request of any Holder of
Registrable Securities in connection with that Holder's sale pursuant to Rule
144, the Issuer shall



                                      -19-
<PAGE>   20



deliver to such Holder a written statement as to whether it has complied with
such requirements. If the Issuer ever ceases to be subject to the reporting
requirements of the Exchange Act, it will deliver to the Holders and prospective
purchasers the information required to be delivered pursuant to Rule 144A(d)(4)
under the Securities Act.

         9. Miscellaneous.

                  (a) Notices. All notices, requests, claims, demands, waivers
         and other communications hereunder shall be in writing and effective
         only on receipt, and if sent to the Issuer, will be mailed, delivered
         or telefaxed to 1400 Smith Street, Houston, Texas, 77002, Attention:
         Ben Glisan, Managing Director and Treasurer, Facsimile No. (713)
         646-4990, if to an Initial Purchaser, to it at the address for the
         Initial Purchasers set forth in the Purchase Agreement; and if to a
         Holder, will be mailed, delivered to telefaxed to the address of such
         Holder set forth in the security register, a Notice and Questionnaire
         or other records of the Issuer or to such other address as the Issuer
         or any such Holder may have furnished to the other in writing in
         accordance herewith, except that notices of change of address shall be
         effective only upon receipt.

                  (b) Parties in Interest. All the terms and provisions of this
         Agreement shall be binding upon, shall inure to the benefit of and
         shall be enforceable by the respective successors and assigns of the
         parties hereto. In the event that any transferee of any Holder of
         Registrable Securities shall acquire Registrable Securities, in any
         manner, whether by gift, bequest, purchase, operation of law or
         otherwise, such transferee shall, without any further writing or action
         of any kind, be deemed a party hereto for all purposes and such
         Registrable Securities shall be held subject to all of the terms of
         this Agreement, and by taking and holding such Registrable Securities
         such transferee shall be entitled to receive the benefits of, and be
         conclusively deemed to have agreed to be bound by and to perform, all
         of the applicable terms and provisions of this Agreement.

                  (c) Survival. The respective agreements, representations,
         warranties, indemnities and other statements of the Issuer or its
         officers and directors and of the Holders set forth or made pursuant to
         this Agreement shall remain in full force and effect regardless of any
         investigation (or statement as to the results thereof) made by or on
         behalf of any Holder, the Issuer, any agent or underwriter or any
         director, principal, partner, officer, or any controlling Person of any
         of the foregoing, and shall survive delivery of and payment for the
         Securities pursuant to the Purchase Agreement and the transfer and
         registration of the Securities pursuant to this Agreement. However,
         this Agreement shall terminate and be of no force or effect after the
         Termination Date, except with respect to any obligations under Sections
         2(c), 5 or 7 hereof that relate to events occurring prior to the
         Termination Date.

                  (d) Applicable Law. This Agreement will be governed by and
         construed in accordance with the laws of the Sate of New York
         applicable to contracts made and to be performed within the Sate of New
         York.

                  (e) Headings. The section headings used herein are inserted
         for convenience only and shall not affect the construction hereof.



                                      -20-
<PAGE>   21



                  (f) Entire Agreement; Amendments. This Agreement and the other
         writings referred to herein (including the Purchase Agreement and the
         Indenture) or delivered pursuant hereto which form a part hereof
         contain the entire understanding of the parties with respect to its
         subject matter. This Agreement and the Purchase Agreement supersede all
         prior agreements and understandings between the parties with respect to
         subject matter. This Agreement may be amended and the observance of any
         term of this Agreement may be waived (either generally or in a
         particular instance and either retroactively or prospectively) only by
         a written instrument duly executed by the Issuer and the Holders of at
         least a majority of the Shares constituting Registrable Securities at
         the time outstanding (with Holders of Notes deemed to be the Holders,
         for the purposes of this Section, of the number of outstanding Shares
         into which such Notes are or would be convertible or exchangeable as of
         the date on which such consent is requested). Each Holder of any
         Registrable Securities at the time or thereafter outstanding shall be
         bound by any amendment or waiver effected pursuant to this Section
         9(f), whether or not any notice, writing or marking indicating such
         amendment or waiver appears on such Registrable Securities or is
         delivered to such Holder.

                  (g) Inspection. For so long as this Agreement shall be in
         effect, this Agreement and a complete list of the names and addresses
         of all the Holders of Registrable Securities shall be made available
         for inspection and copying on any business day by any Holder of
         Registrable Securities for proper purposes only (which shall include
         any purpose related to the rights of the Holders of Registrable
         Securities under the Securities, the Indenture and this Agreement) at
         the offices of the Issuer at the address thereof set forth in Section
         9(a) above, or at the office of the Trustee under the Indenture.

                  (h) Counterparts. This Agreement may be executed by one or
         more counterparts, each of which shall constitute an original and all
         of which together shall constitute one and the same instrument.



                                      -21-
<PAGE>   22



         Agreed to and accepted as of the date referred to above.

                                          Very truly yours,

                                          ENRON CORP.



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



                                      -22-
<PAGE>   23



The foregoing Agreement is hereby confirmed and
accepted as of the date first above written.

SALOMON SMITH BARNEY INC.
J.P. MORGAN SECURITIES INC.
DEUTSCHE BANC ALEX. BROWN INC.
BANC OF AMERICA SECURITIES LLC
BARCLAYS CAPITAL INC.

By:  Salomon Smith Barney Inc.


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