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                                                                  Exhibit 4(b)

                          REGISTRATION RIGHTS AGREEMENT


                                     BETWEEN


                                 AON CORPORATION

                                   AS ISSUER,


                                       AND


                       MORGAN STANLEY & CO. INCORPORATED,


                              AS INITIAL PURCHASER


                          DATED AS OF NOVEMBER 7, 2002

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         REGISTRATION RIGHTS AGREEMENT dated as of November 7, 2002 between Aon
Corporation, a Delaware corporation (the "COMPANY"), and Morgan Stanley & Co.
Incorporated (the "INITIAL PURCHASER") pursuant to the Purchase Agreement dated
November 4, 2002 (the "PURCHASE AGREEMENT"), between the Company and the Initial
Purchaser. In order to induce the Initial Purchaser to enter into the Purchase
Agreement, the Company has agreed to provide the registration rights set forth
in this Agreement. The execution of this Agreement is a condition to the closing
under the Purchase Agreement.

         The Company agrees with the Initial Purchaser, (i) for its benefit as
Initial Purchaser and (ii) for the benefit of the beneficial owners (including
the Initial Purchaser) from time to time of the Debentures (as defined herein)
and the beneficial owners from time to time of the Underlying Common Stock (as
defined herein) issued upon conversion of the Debentures (each of the foregoing
a "HOLDER" and together the "HOLDERS"), as follows:

         SECTION 1. DEFINITIONS. Capitalized terms used herein without
definition shall have their respective meanings set forth in the Purchase
Agreement. As used in this Agreement, the following terms shall have the
following meanings:

         "AFFILIATE" means with respect to any specified person, an "affiliate,"
as defined in Rule 144, of such person.

         "AMENDMENT EFFECTIVENESS DEADLINE DATE" has the meaning set forth in
Section 2(d) hereof.

         "BUSINESS DAY" means each Monday, Tuesday, Wednesday, Thursday and
Friday that is not a day on which banking institutions in The City of New York
are authorized or obligated by law or executive order to close.

         "COMMON STOCK" means the shares of common stock, par value $1.00 per
share, of the Company and any other shares of common stock as may constitute
"Common Stock" for purposes of the Indenture, including the Underlying Common
Stock.

         "CONVERSION PRICE" has the meaning assigned such term in the Indenture.

         "DAMAGES ACCRUAL PERIOD" has the meaning set forth in Section 2(e)
hereof.

         "DAMAGES PAYMENT DATE" means each May 15 and November 15.

         "DEBENTURES" means the 3 1/2% Senior Convertible Debentures Due 2012 of
the Company to be purchased pursuant to the Purchase Agreement.

         "DEFERRAL NOTICE" has the meaning set forth in Section 3(h) hereof.

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         "DEFERRAL PERIOD" has the meaning set forth in Section 3(h) hereof.

         "EFFECTIVENESS DEADLINE DATE" has the meaning set forth in Section 2(a)
hereof.

         "EFFECTIVENESS PERIOD" means the period commencing on the date hereof
and ending on the date that all Registrable Securities have ceased to be
Registrable Securities.

         "EVENT" has the meaning set forth in Section 2(e) hereof.

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

         "FILING DEADLINE DATE" has the meaning set forth in Section 2(a)
hereof.

         "HOLDER" has the meaning set forth in the second paragraph of this
Agreement.

         "INDENTURE" means the Indenture, dated as of November 7, 2002, between
the Company and The Bank of New York, as trustee, pursuant to which the
Debentures are being issued.

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

         "INITIAL SHELF REGISTRATION STATEMENT" has the meaning set forth in
Section 2(a) hereof.

         "ISSUE DATE" means November 7, 2002.

         "LIQUIDATED DAMAGES AMOUNT" has the meaning set forth in Section 2(e)
hereof.

         "MATERIAL EVENT" has the meaning set forth in Section 3(h) hereof.

         "NOTICE AND QUESTIONNAIRE" means a written notice delivered to the
Company containing substantially the information called for by the Selling
Securityholder Notice and Questionnaire attached as Annex A to the Offering
Memorandum of the Company dated November 4, 2002 relating to the Debentures.

         "NOTICE HOLDER" means, on any date, any Holder that has delivered a
Notice and Questionnaire to the Company on or prior to such date.

         "PURCHASE AGREEMENT" has the meaning set forth in the preamble hereof.

         "PROSPECTUS" means the prospectus included in any Registration
Statement (including, without limitation, a prospectus that discloses
information previously omitted from a prospectus filed as part of an effective
registration statement in reliance upon Rule 430A promulgated under

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the Securities Act), 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.

         "RECORD HOLDER" means with respect to any Damages Payment Date relating
to any Debentures or Underlying Common Stock as to which any Liquidated Damages
Amount has accrued, the registered holder of such Debenture or Underlying Common
Stock on the May 1 immediately preceding a Damages Payment Date occurring on a
May 15, and on the November 1 immediately preceding a Damages Payment Date
occurring on a November 15.

         "REGISTRABLE SECURITIES" means the Debentures until such Debentures
have been converted into or exchanged for the Underlying Common Stock and, at
all times subsequent to any such conversion, the Underlying Common Stock and any
securities into or for which such Underlying Common Stock has been converted or
exchanged, and any security issued with respect thereto upon any stock dividend,
split or similar event until, in the case of any such security, (A) the earliest
of (i) its effective registration under the Securities Act and resale in
accordance with the Registration Statement covering it, (ii) expiration of the
holding period that would be applicable thereto, under Rule 144(k) or (iii) its
sale to the public pursuant to Rule 144 (or any similar provision then in force,
but not Rule 144A) under the Securities Act, and (B) as a result of the event or
circumstance described in any of the foregoing clauses (i) through (iii), the
legend with respect to transfer restrictions required under the Indenture is
removed or removable in accordance with the terms of the Indenture or such
legend, as the case may be.

         "REGISTRATION STATEMENT" means any registration statement of the
Company that covers any of the Registrable Securities pursuant to the provisions
of this Agreement, including the Prospectus, amendments and supplements to such
registration statement, including post-effective amendments, all exhibits and
all materials incorporated by reference or explicitly deemed to be incorporated
by reference in such registration statement.

         "RESTRICTED SECURITIES" means "Restricted Securities" as defined in
Rule 144.

         "RULE 144" means Rule 144 under the Securities Act, as such Rule may be
amended from time to time, or any similar rule or regulation hereafter adopted
by the SEC.

         "RULE 144A" means Rule 144A under the Securities Act, as such Rule may
be amended from time to time, or any similar rule or regulation hereafter
adopted by the SEC.

         "SEC" means the Securities and Exchange Commission.

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

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         "SHELF REGISTRATION STATEMENT" has the meaning set forth in Section
2(a) hereof.

         "SPECIAL COUNSEL" means Davis Polk & Wardwell or one such other
successor counsel as shall be specified by the Holders of a majority of the
Registrable Securities, but which may, with the written consent of the Initial
Purchaser (which shall not be unreasonably withheld), be another nationally
recognized law firm experienced in securities law matters designated by the
Company, the reasonable fees and expenses of which will be paid by the Company
pursuant to Section 5 hereof. For purposes of determining the holders of a
majority of the Registrable Securities in this definition, Holders of Debentures
shall be deemed to be the Holders of the number of shares of Underlying Common
Stock into which such Debentures are or would be convertible as of the date the
consent is requested.

         "SUBSEQUENT SHELF REGISTRATION STATEMENT" has the meaning set forth in
Section 2(b) hereof.

         "TIA" means the Trust Indenture Act of 1939, as amended.

         "TRUSTEE" means The Bank of New York, the Trustee under the Indenture.

         "UNDERLYING COMMON STOCK" means the Common Stock into which the
Debentures are convertible or issued upon any such conversion.

         SECTION 2. SHELF REGISTRATION. (a) The Company shall prepare and file
or cause to be prepared and filed with the SEC, as soon as practicable but in
any event by the date (the "FILING DEADLINE DATE") ninety (90) days after the
Issue Date, a Registration Statement for an offering to be made on a delayed or
continuous basis pursuant to Rule 415 of the Securities Act (a "SHELF
REGISTRATION STATEMENT") registering the resale from time to time by Holders
thereof of all of the Registrable Securities (the "INITIAL SHELF REGISTRATION
STATEMENT"). The Initial Shelf Registration Statement shall be on Form S-3 or
another appropriate form permitting registration of such Registrable Securities
for resale by such Holders in accordance with the methods of distribution
elected by the Holders and set forth in the Initial Shelf Registration
Statement. The Company shall use its reasonable best efforts to cause the
Initial Shelf Registration Statement to be declared effective under the
Securities Act as promptly as is practicable but in any event by the date (the
"EFFECTIVENESS DEADLINE DATE") that is one hundred eighty (180) days after the
Issue Date, and to keep the Initial Shelf Registration Statement (or any
Subsequent Shelf Registration Statement) continuously effective under the
Securities Act until the expiration of the Effectiveness Period. At the time the
Initial Shelf Registration Statement is declared effective, each Holder that
became a Notice Holder on or prior to the date ten (10) Business Days prior to
such time of effectiveness shall be named as a selling securityholder in the
Initial Shelf Registration Statement and the related Prospectus in such a manner
as to permit such Holder to deliver such Prospectus to purchasers of Registrable
Securities in accordance with applicable law. None of the Company's security
holders (other than the Holders of Registrable Securities)

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shall have the right to include any of the Company's securities in the Shelf
Registration Statement.

          (b) If the Initial Shelf Registration Statement or any Subsequent
Shelf Registration Statement ceases to be effective for any reason at any time
during the Effectiveness Period (other than because all Registrable Securities
registered thereunder shall have been resold pursuant thereto or shall have
otherwise ceased to be Registrable Securities), the Company shall use its
reasonable best efforts to obtain the prompt withdrawal of any order suspending
the effectiveness thereof, and in any event shall within thirty (30) days of
such cessation of effectiveness amend the Shelf Registration Statement in a
manner reasonably expected to obtain the withdrawal of the order suspending the
effectiveness thereof, or file an additional Shelf Registration Statement
covering all of the securities that as of the date of such filing are
Registrable Securities (a "SUBSEQUENT SHELF REGISTRATION STATEMENT"). If a
Subsequent Shelf Registration Statement is filed, the Company shall use its
reasonable best efforts to cause the Subsequent Shelf Registration Statement to
become effective as promptly as is practicable after such filing and to keep
such Registration Statement (or subsequent Shelf Registration Statement)
continuously effective until the end of the Effectiveness Period.

          (c) The Company shall supplement and amend the Shelf Registration
Statement if required by the rules, regulations or instructions applicable to
the registration form used by the Company for such Shelf Registration Statement,
if required by the Securities Act or as necessary to name a Notice Holder as a
selling securityholder pursuant to Section (d) below.

          (d) Each Holder agrees that if such Holder wishes to sell Registrable
Securities pursuant to a Shelf Registration Statement and related Prospectus, it
will do so only in accordance with this Section 2(d) and Section 3(h). Following
the date that the Initial Shelf Registration Statement is declared effective,
each Holder wishing to sell Registrable Securities pursuant to a Shelf
Registration Statement and related Prospectus agrees to deliver a Notice and
Questionnaire to the Company at least three (3) Business Days prior to any
intended distribution of Registrable Securities under the Shelf Registration
Statement. Each holder who elects to sell Registrable Securities pursuant to a
Shelf Registration Statement agrees by submitting a Notice and Questionnaire to
the Company, it will be bound by the terms and conditions of the Notice and
Questionnaire and this Agreement. From and after the date the Initial Shelf
Registration Statement is declared effective, the Company shall, as promptly as
practicable after the date a Notice and Questionnaire is delivered pursuant to
Section 8(c) hereof, and in any event upon the later of (x) five (5) Business
Days after such date or (y) five (5) Business Days after the expiration of any
Deferral Period in effect when the Notice and Questionnaire is delivered or put
into effect within five (5) Business Days of such delivery date:

                (i) if required by applicable law, file with the SEC a
          post-effective amendment to the Shelf Registration Statement or
          prepare and, if required by applicable law, file a supplement to the
          related Prospectus or a supplement or amendment to any document

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          incorporated therein by reference or file any other required
          document so that the Holder delivering such Notice and
          Questionnaire is named as a selling securityholder in the Shelf
          Registration Statement and the related Prospectus in such a
          manner as to permit such Holder to deliver such Prospectus to
          purchasers of the Registrable Securities in accordance with
          applicable law and, if the Company shall file a post-effective
          amendment to the Shelf Registration Statement, use its reasonable
          best efforts to cause such post-effective amendment to be
          declared effective under the Securities Act as promptly as is
          practicable, but in any event by the date (the "AMENDMENT
          EFFECTIVENESS DEADLINE DATE") that is forty-five (45) days after
          the date such post-effective amendment is required by this clause
          to be filed;

                (ii) provide such Holder copies of any documents filed pursuant
          to Section 2(d)(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(d)(i);

PROVIDED, that if such Notice and Questionnaire is delivered during a Deferral
Period, the Company shall so inform the Holder delivering such Notice and
Questionnaire 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(h). Notwithstanding anything contained herein to the contrary, (i) the Company
shall be under no obligation to name any Holder that is not a Notice Holder as a
selling securityholder in any Registration Statement or related Prospectus and
(ii) the Amendment Effectiveness Deadline Date shall be extended by up to ten
(10) Business Days from the expiration of a Deferral Period (and the Company
shall incur no obligation to pay Liquidated Damages during such extension or
during such Deferral Period) if such Deferral Period shall be in effect on the
Amendment Effectiveness Deadline Date.

          (e) The parties hereto agree that the Holders of Registrable
Securities will suffer damages, and that it would not be feasible to ascertain
the extent of such damages with precision, if, other than as permitted
hereunder,

                  (i) the Initial Shelf Registration Statement has not been
         filed on or prior to the Filing Deadline Date,

                 (ii) the Initial Shelf Registration Statement has not been
         declared effective under the Securities Act on or prior to the
         Effectiveness Deadline Date,

                (iii) the Company has failed to perform its obligations set
         forth in Section 2(d)(i) within the time period required therein,

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                 (iv) any post-effective amendment to a Shelf Registration
         Statement filed pursuant to Section 2(d)(i) has not become effective
         under the Securities Act on or prior to the Amendment Effectiveness
         Deadline Date, or

                  (v) the aggregate duration of Deferral Periods in any period
         exceeds the number of days permitted in respect of such period pursuant
         to Section 3(h) hereof.

Each event described in any of the foregoing clauses (i) through (v) is
individually referred to herein as an "EVENT." For purposes of this Agreement,
each Event set forth above shall begin and end on the dates set forth in the
table set forth below:

<Table>
<Caption>

              Type of
              Event by                            Beginning                           Ending
               Clause                               Date                               Date
------------------------------------- ---------------------------------- ----------------------------------
<S>           <C>                     <C>                                <C>

                (i)                   Filing Deadline Date               the date the Initial Shelf
                                                                         Registration Statement is filed

                (ii)                  Effectiveness Deadline Date        the date the Initial Shelf
                                                                         Registration Statement becomes
                                                                         effective under the Securities
                                                                         Act

               (iii)                  the date by which the Company is   the date the Company performs
                                      required to perform its            its obligations set forth in
                                      obligations under Section 2(d)     Section 2(d)

                (iv)                  the Amendment Effectiveness        the date the applicable
                                      Deadline Date                      post-effective amendment to a
                                                                         Shelf Registration Statement
                                                                         becomes effective under the
                                                                         Securities Act

                (v)                   the date on which the aggregate    termination of the Deferral
                                      duration of Deferral Periods in    Period that caused the limit on
                                      any period exceeds the number of   the aggregate duration of
                                      days permitted by Section 3(h)     Deferral Periods to be exceeded
</Table>

For purposes of this Agreement, Events shall begin on the dates set forth in the
table above and shall continue until the ending dates set forth in the table
above.

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         Commencing on (and including) any date that an Event has begun and
ending on (but excluding) the next date on which there are no Events that have
occurred and are continuing (a "DAMAGES ACCRUAL PERIOD"), the Company shall pay,
as liquidated damages and not as a penalty, to Record Holders of Registrable
Securities an amount (the "LIQUIDATED DAMAGES AMOUNT") accruing, for each day in
the Damages Accrual Period, (i) in respect of any Debenture, at a rate per annum
equal to 0.25% for the first 90 day period after the occurrence of such an Event
and 0.5% thereafter, of the aggregate principal amount of such Debenture and
(ii) in respect of each share of Underlying Common Stock at a rate per annum
equal to 0.25% for the first 90 day period after the occurrence of such an Event
and 0.5% thereafter, on the Conversion Price on such date, as the case may be;
PROVIDED that in the case of a Damages Accrual Period that is in effect solely
as a result of an Event of the type described in clause (iii) or (iv) of the
preceding paragraph, such Liquidated Damages Amount shall be paid only to the
Holders (as set forth in the succeeding paragraph) that have delivered Notices
and Questionnaires that caused the Company to incur the obligations set forth in
Section 2(d) the non-performance of which is the basis of such Event. In
calculating the Liquidated Damages Amount on any date on which no Debentures are
outstanding, the Conversion Price and the Liquidated Damages Amount payable with
respect to shares of Common Stock which are Registrable Securities, shall be
calculated as if the Debentures were still outstanding. Notwithstanding the
foregoing, no Liquidated Damages Amount shall accrue as to any Registrable
Security from and after the earlier of (x) the date such security is no longer a
Registrable Security and (y) expiration of the Effectiveness Period. The rate of
accrual of the Liquidated Damages Amount with respect to any period shall not
exceed the rate provided for in this paragraph notwithstanding the occurrence of
multiple concurrent Events.

         The Liquidated Damages Amount shall accrue from the first day of the
applicable Damages Accrual Period, and shall be payable on each Damages Payment
Date during the Damage Accrual Period (and on the Damages Payment Date next
succeeding the end of the Damages Accrual Period if the Damage Accrual Period
does not end on a Damages Payment Date) to the Record Holders of the Registrable
Securities entitled thereto; PROVIDED that any Liquidated Damages Amount accrued
with respect to any Debenture or portion thereof redeemed by the Company on a
redemption date or converted into Underlying Common Stock on a conversion date
prior to the Damages Payment Date, shall, in any such event, be paid instead to
the Holder who submitted such Debenture or portion thereof for redemption or
conversion on the applicable redemption date or conversion date, as the case may
be, on such date (or promptly following the conversion date, in the case of
conversion); PROVIDED FURTHER, that, in the case of an Event of the type
described in clause (iii) or (iv) of the first paragraph of this Section 2(e),
such Liquidated Damages Amount shall be paid only to the Holders entitled
thereto pursuant to such first paragraph by check mailed to the address set
forth in the Notice and Questionnaire delivered by such Holder. The Trustee
shall be entitled, on behalf of registered holders of Debentures or Underlying
Common Stock, to seek any available remedy for the enforcement of this
Agreement, including for the payment of such Liquidated Damages Amount.
Notwithstanding the foregoing, the parties agree that the sole damages payable
for a violation of the terms of this Agreement

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with respect to which liquidated damages are expressly provided shall be such
liquidated damages. Nothing shall preclude any Holder from pursuing or obtaining
specific performance or other equitable relief with respect to this Agreement.

         All of the Company's obligations set forth in this Section 2(e) that
are outstanding with respect to any Registrable Security at the time such
security ceases to be a Registrable Security shall survive until such time as
all such obligations with respect to such security have been satisfied in full
(notwithstanding termination of this Agreement pursuant to Section 8(k)).

         The parties hereto agree that the liquidated damages provided for in
this Section 2(e) constitute a reasonable estimate of the damages that may be
incurred by Holders of Registrable Securities by reason of the failure of the
Shelf Registration Statement to be filed or declared effective or available for
effecting resales of Registrable Securities in accordance with the provisions
hereof.

         SECTION 3. REGISTRATION PROCEDURES. In connection with the registration
obligations of the Company under Section 2 hereof, during the Effectiveness
Period, the Company shall:

                  (a) Prepare and file with the SEC a Registration Statement or
         Registration Statements on any appropriate form under the Securities
         Act available for the sale of the Registrable Securities by the Holders
         thereof in accordance with the intended method or methods of
         distribution thereof, and use its reasonable best efforts to cause each
         such Registration Statement to become effective and remain effective as
         provided herein; PROVIDED that before filing any Registration Statement
         or Prospectus or any amendments or supplements thereto with the SEC
         (but excluding reports filed with the SEC under the Exchange Act),
         furnish to the Initial Purchaser and the Special Counsel of such
         offering, if any, copies of all such documents proposed to be filed at
         least three (3) Business Days prior to the filing of such Registration
         Statement or amendment thereto or Prospectus or supplement thereto.

                  (b) Subject to Section 3(h), prepare and file with the SEC
         such amendments and post-effective amendments to each Registration
         Statement as may be necessary to keep such Registration Statement
         continuously effective for the applicable period specified in Section
         2(a); cause the related Prospectus to be supplemented by any required
         prospectus supplement, and as so supplemented to be filed pursuant to
         Rule 424 (or any similar provisions then in force) under the Securities
         Act; and use its reasonable best efforts to comply with the provisions
         of the Securities Act applicable to it with respect to the disposition
         of all securities covered by such Registration Statement during the
         Effectiveness Period in accordance with the intended methods of
         disposition by the sellers thereof set forth in such Registration
         Statement as so amended or such Prospectus as so supplemented.

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                  (c) As promptly as practicable give notice to the Notice
         Holders, the Initial Purchaser and the Special Counsel, (i) when any
         Prospectus, prospectus supplement, Registration Statement or
         post-effective amendment to a Registration Statement has been filed
         with the SEC and, with respect to a Registration Statement or any
         post-effective amendment, when the same has been declared effective,
         (ii) of any request, following the effectiveness of the Initial Shelf
         Registration Statement under the Securities Act, by the SEC or any
         other federal or state governmental authority for amendments or
         supplements to any Registration Statement or related Prospectus or for
         additional information relating to the Shelf Registration Statement,
         (iii) of the issuance by the SEC or any other federal or state
         governmental authority of any stop order suspending the effectiveness
         of any Registration Statement or the initiation or threatening of any
         proceedings for that purpose, (iv) of the receipt by the Company of any
         notification with respect to the suspension of the qualification or
         exemption from qualification of any of the Registrable Securities for
         sale in any jurisdiction or the initiation or threatening of any
         proceeding for such purpose, (v) of the occurrence of, but not the
         nature of or details concerning, a Material Event and (vi) of the
         determination by the Company that a post-effective amendment to a
         Registration Statement will be filed with the SEC, which notice may, at
         the discretion of the Company (or as required pursuant to Section
         3(h)), state that it constitutes a Deferral Notice, in which event the
         provisions of Section 3(h) shall apply.

                  (d) Use its reasonable best efforts to obtain the withdrawal
         of any order suspending the effectiveness of a Registration Statement
         or the lifting of any suspension of the qualification (or exemption
         from qualification) of any of the Registrable Securities for sale in
         any jurisdiction in which they have been qualified for sale, in either
         case at the earliest possible moment, and provide immediate notice to
         each Notice Holder and the Initial Purchaser of the withdrawal of any
         such order.

                  (e) As promptly as practicable furnish to each Notice Holder,
         the Special Counsel and the Initial Purchaser, upon request and without
         charge, at least one (1) conformed copy of the Registration Statement
         and any amendment thereto, including exhibits and if requested, all
         documents incorporated or deemed to be incorporated therein by
         reference.

                  (f) During the Effectiveness Period, deliver to each Notice
         Holder, the Special Counsel, if any, and the Initial Purchaser, in
         connection with any sale of Registrable Securities pursuant to a
         Registration Statement, without charge, as many copies of the
         Prospectus or Prospectuses relating to such Registrable Securities
         (including each preliminary prospectus) and any amendment or supplement
         thereto as such Notice Holder may reasonably request; and the Company
         hereby consents (except during such periods that a Deferral Notice is
         outstanding and has not been revoked) to the use of such Prospectus or
         each amendment or supplement thereto by each Notice Holder in

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         connection with any offering and sale of the Registrable Securities
         covered by such Prospectus or any amendment or supplement thereto in
         the manner set forth therein.

                  (g) Prior to any public offering of the Registrable Securities
         pursuant to a Registration Statement, use its reasonable best efforts
         to register or qualify or cooperate with the Notice Holders and the
         Special Counsel in connection with the registration or qualification
         (or exemption from such registration or qualification) of such
         Registrable Securities for offer and sale under the securities or Blue
         Sky laws of such jurisdictions within the United States as any Notice
         Holder reasonably requests in writing (which request may be included in
         the Notice and Questionnaire); prior to any public offering of the
         Registrable Securities pursuant to the Shelf Registration Statement,
         use its reasonable best efforts to keep each such registration or
         qualification (or exemption therefrom) effective during the
         Effectiveness Period in connection with such Notice Holder's offer and
         sale of Registrable Securities pursuant to such registration or
         qualification (or exemption therefrom) and do any and all other acts or
         things reasonably necessary or advisable to enable the disposition in
         such jurisdictions of such Registrable Securities in the manner set
         forth in the relevant Registration Statement and the related
         Prospectus; PROVIDED that the Company will not be required to (i)
         qualify as a foreign corporation or as a dealer in securities in any
         jurisdiction where it would not otherwise be required to qualify but
         for this Agreement or (ii) take any action that would subject it to
         general service of process in suits or to taxation in any such
         jurisdiction where it is not then so subject.

                  (h) Upon (A) the issuance by the SEC of a stop order
         suspending the effectiveness of the Shelf Registration Statement or the
         initiation of proceedings with respect to the Shelf Registration
         Statement under Section 8(d) or 8(e) of the Securities Act, (B) the
         occurrence of any event or the existence of any fact (a "MATERIAL
         EVENT") as a result of which any Registration Statement 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, or (C) the occurrence or existence of any pending
         corporate development that, in the reasonable discretion of the
         Company, makes it appropriate to suspend the availability of the Shelf
         Registration Statement and the related Prospectus:

                     (i) in the case of clause (B) above, subject to the next
               sentence, as promptly as practicable prepare and file, if
               necessary pursuant to applicable law, a post-effective amendment
               to such Registration Statement 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

                                       12
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               Registration Statement and Prospectus so that such Registration
               Statement 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 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 Registration Statement,
               subject to the next sentence, use its reasonable best efforts to
               cause it to be declared effective as promptly as is practicable,
               and

                     (ii) give notice to the Notice Holders, and the Special
               Counsel, if any, that the availability of the Shelf Registration
               Statement 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 Registration
               Statement until such Notice Holder's receipt of copies of the
               supplemented or amended Prospectus provided for in clause (i)
               above, or until it is advised in writing by the Company 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 Company will use its reasonable best efforts to ensure that the use of the
Prospectus may be resumed (x) in the case of clause (A) above, as promptly as is
practicable, (y) in the case of clause (B) above, as soon as, in the sole
judgment of the Company, public disclosure of such Material Event would not be
prejudicial to or contrary to the interests of the Company or, if necessary to
avoid unreasonable burden or expense, as soon as practicable thereafter and (z)
in the case of clause (C) above, as soon as in the reasonable discretion of the
Company, such suspension is no longer appropriate. The Company shall be entitled
to exercise its right under this Section 3(h) to suspend the availability of the
Shelf Registration Statement or any Prospectus, without incurring or accruing
any obligation to pay liquidated damages pursuant to Section 2(e) (the "DEFERRAL
PERIOD"); PROVIDED that the aggregate duration of any Deferral Periods shall not
exceed 30 days in any three month period (or 60 days in any three month period
in the event of a Material Event pursuant to which the Company has delivered a
second notice as required below) or 90 days in any twelve (12) month period;
PROVIDED that in the case of a Material Event relating to an acquisition or a
probable acquisition or financing, recapitalization, business combination or
other similar transaction, the Company may, without incurring any obligation to
pay liquidated damages pursuant to Section 2(e), deliver to Notice Holders a
second notice to the effect set forth above, which shall have the effect of
extending the Deferral Period by up to an additional 30 days, or such shorter
period of time as is specified in such second notice.

                                       13
<Page>

                  (i) If reasonably requested in writing in connection with a
         disposition of Registrable Securities pursuant to a Registration
         Statement, make reasonably available for inspection during normal
         business hours by a representative for the Notice Holders of such
         Registrable Securities, any broker-dealers, attorneys and accountants
         retained by such Notice Holders, and any attorneys or other agents
         retained by a broker-dealer engaged by such Notice Holders, all
         relevant financial and other records and pertinent corporate documents
         and properties of the Company and its subsidiaries, and cause the
         appropriate officers, directors and employees of the Company and its
         subsidiaries to make reasonably available for inspection during normal
         business hours on reasonable notice all relevant information reasonably
         requested by such representative for the Notice Holders, or any such
         broker-dealers, attorneys or accountants in connection with such
         disposition, in each case as is customary for similar "due diligence"
         examinations; PROVIDED that such persons shall first agree in writing
         with the Company that any information that is reasonably designated by
         the Company as confidential at the time of delivery of such information
         shall be kept confidential by such persons and shall be used solely for
         the purposes of exercising rights under this Agreement, unless (i)
         disclosure of such information is required by court or administrative
         order or is necessary to respond to inquiries of regulatory
         authorities, (ii) disclosure of such information is required by law
         (including any disclosure requirements pursuant to federal securities
         laws in connection with the filing of any Registration Statement or the
         use of any prospectus referred to in this Agreement), (iii) such
         information becomes generally available to the public other than as a
         result of a disclosure or failure to safeguard by any such person or
         (iv) such information becomes available to any such person from a
         source other than the Company and such source is not bound by a
         confidentiality agreement, and PROVIDED FURTHER that the foregoing
         inspection and information gathering shall, to the greatest extent
         possible, be coordinated on behalf of all the Notice Holders and the
         other parties entitled thereto by the counsel referred to in Section 5.
         Any person legally compelled to disclose any such confidential
         information made available for inspection shall provide the Company
         with prompt prior written notice of such requirement so that the
         Company may seek a protective order or other appropriate remedy.

                  (j) Comply with all applicable rules and regulations of the
         SEC and make generally available to its securityholders earning
         statements (which need not be audited) satisfying the provisions of
         Section 11(a) of the Securities Act and Rule 158 thereunder (or any
         similar rule promulgated under the Securities Act) for a 12-month
         period commencing on the first day of the first fiscal quarter of the
         Company commencing after the effective date of a Registration
         Statement, which statements shall be made available no later than 45
         days after the end of the 12-month period or 90 days if the 12-month
         period coincides with the fiscal year of the Company.

                  (k) Cooperate with each Notice Holder to facilitate the timely
         preparation and delivery of certificates representing Registrable
         Securities sold or to be sold pursuant to a

                                       14
<Page>

         Registration Statement, which certificates shall not bear any
         restrictive legends, and cause such Registrable Securities to be in
         such denominations as are permitted by the Indenture and registered in
         such names as such Notice Holder may request in writing at least two
         (2) Business Day prior to any sale of such Registrable Securities.

                  (l) Provide a CUSIP number for all Registrable Securities
         covered by each Registration Statement not later than the effective
         date of such Registration Statement and provide the Trustee and the
         transfer agent for the Common Stock with printed certificates for the
         Registrable Securities that are in a form eligible for deposit with The
         Depository Trust Company.

                  (m) Cooperate and assist in any filings required to be made
         with the National Association of Securities Dealers, Inc.

                  (n) Upon (i) the filing of the Initial Shelf Registration
         Statement and (ii) the effectiveness of the Initial Shelf Registration
         Statement, announce the same, in each case by release to Reuters
         Economic Services and Bloomberg Business News.

         SECTION 4. HOLDER'S OBLIGATIONS. Each Holder agrees, by acquisition of
the Registrable Securities, that no Holder shall be entitled to sell any of such
Registrable Securities pursuant to a Registration Statement or to receive a
Prospectus relating thereto, unless such Holder has furnished the Company with a
Notice and Questionnaire as required pursuant to Section 2(d) 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 Company all information required to be disclosed in
order to make the information previously furnished to the Company by such Notice
Holder not misleading and any other information regarding such Notice Holder and
the distribution of such Registrable Securities as the Company may from time to
time reasonably request. Any sale of any Registrable Securities by any Holder
shall constitute a representation and warranty by such Holder that the
information relating to such Holder and its plan of distribution is as set forth
in the Prospectus delivered by such Holder in connection with such disposition,
that such Prospectus does not as of the time of such sale contain any untrue
statement of a material fact relating to or provided by such Holder or its plan
of distribution and that such Prospectus does not as of the time of such sale
omit to state any material fact relating to or provided by such Holder or its
plan of distribution necessary to make the statements in such Prospectus, in the
light of the circumstances under which they were made, not misleading.

         SECTION 5. REGISTRATION EXPENSES. The Company shall bear all fees and
expenses incurred in connection with the performance by the Company of its
obligations under Sections 2 and 3 of this Agreement whether or not any
Registration Statement is declared effective. Such fees and expenses shall
include, without limitation, (i) all registration and filing fees (including,
without limitation, fees and expenses (x) with respect to filings required to be
made with the

                                       15
<Page>

National Association of Securities Dealers, Inc. and (y) of compliance with
federal and state securities or Blue Sky laws (including, without limitation,
reasonable fees and disbursements of the Special Counsel in connection with Blue
Sky qualifications of the Registrable Securities under the laws of such
jurisdictions as Notice Holders of a majority of the Registrable Securities
being sold pursuant to a Registration Statement may designate), (ii) printing
expenses (including, without limitation, expenses of printing certificates for
Registrable Securities in a form eligible for deposit with The Depository Trust
Company), (iii) duplication expenses relating to copies of any Registration
Statement or Prospectus delivered to any Holders hereunder, (iv) fees and
disbursements of counsel for the Company in connection with the Shelf
Registration Statement, (v) reasonable fees and disbursements of the Trustee and
its counsel and of the registrar and transfer agent for the Common Stock and
(vi) any Securities Act liability insurance obtained by the Company in its sole
discretion. In addition, the Company shall pay the internal expenses of the
Company (including, without limitation, all salaries and expenses of officers
and employees performing legal or accounting duties), the expense of any annual
audit, the fees and expenses incurred in connection with the listing by the
Company of the Registrable Securities on any securities exchange on which
similar securities of the Company are then listed and the fees and expenses of
any person, including special experts, retained by the Company. Notwithstanding
the provisions of this Section 5, each seller of Registrable Securities shall
pay selling expenses, including any underwriting discount and commissions, and
all registration expenses to the extent required by applicable law.

         SECTION 6.  INDEMNIFICATION AND CONTRIBUTION.

          (a) INDEMNIFICATION BY THE COMPANY. The Company agrees to indemnify
and hold harmless each Notice Holder, each person, if any, who controls any
Notice Holder within the meaning of either Section 15 of the Securities Act or
Section 20 of the Exchange Act, from and against any and all losses, claims,
damages and liabilities (including, without limitation, any legal or other
expenses reasonably incurred in connection with defending or investigating any
such action or claim) caused by any untrue statement or alleged untrue statement
of a material fact contained in any Registration Statement or any amendment
thereof, any preliminary prospectus or the Prospectus (as amended or
supplemented if the Company shall have furnished any amendments or supplements
thereto), caused by any omission or alleged omission to state therein a material
fact required to be stated therein or necessary to make the statements therein
not misleading, except insofar as such losses, claims, damages or liabilities
are caused by any such untrue statement or omission or alleged untrue statement
or omission based upon information relating to any Holder furnished to the
Company in writing by such Holder expressly for use therein; PROVIDED that the
indemnification contained in this paragraph shall not inure to the benefit of
any Holder (or to the benefit of any person controlling such Holder) on account
of any such losses, claims, damages or liabilities caused by any untrue
statement or alleged untrue statement or omission or alleged omission made in
any preliminary prospectus provided in each case the Company has performed its
obligations under Section 3(a) hereof if either (A) (i) such Holder failed to
send or deliver a copy of the Prospectus with or prior to the delivery of
written

                                       16
<Page>

confirmation of the sale by such Holder to the person asserting the claim from
which such losses, claims, damages or liabilities arise and (ii) the Prospectus
would have corrected such untrue statement or alleged untrue statement or such
omission or alleged omission, or (B) (x) such untrue statement or alleged untrue
statement, omission or alleged omission is corrected in an amendment or
supplement to the Prospectus and (y) having previously been furnished by or on
behalf of the Company with copies of the Prospectus as so amended or
supplemented, such Holder thereafter fails to deliver such Prospectus as so
amended or supplemented, with or prior to the delivery of written confirmation
of the sale of a Registrable Security to the person asserting the claim from
which such losses, claims, damages or liabilities arise.

          (b) INDEMNIFICATION BY HOLDERS. Each Holder agrees severally and not
jointly to indemnify and hold harmless the Company and its directors, its
officers and each person, if any, who controls the Company (within the meaning
of either Section 15 of the Securities Act or Section 20 of the Exchange Act) or
any other Holder, to the same extent as the foregoing indemnity from the Company
to such Holder, but only with reference to information relating to such Holder
furnished to the Company in writing by such Holder expressly for use in such
Registration Statement or Prospectus or amendment or supplement thereto. In no
event shall the liability of any Holder hereunder be greater in amount than the
dollar amount of the proceeds received by such Holder upon the sale of the
Registrable Securities pursuant to the Registration Statement giving rise to
such indemnification obligation.

          (c) CONDUCT OF INDEMNIFICATION PROCEEDINGS. In case any proceeding
(including any governmental investigation) shall be instituted involving any
person in respect of which indemnity may be sought pursuant to Section 6(a) or
6(b) hereof, such person (the "INDEMNIFIED PARTY") shall promptly notify the
person against whom such indemnity may be sought (the "INDEMNIFYING PARTY") in
writing and the indemnifying party, upon request of the indemnified party, shall
retain counsel reasonably satisfactory to the indemnified party to represent the
indemnified party and any others the indemnifying party may designate in such
proceeding and shall pay the reasonable fees and disbursements of such counsel
related to such proceeding. In any such proceeding, any indemnified party shall
have the right to retain its own counsel, but the fees and expenses of such
counsel shall be at the expense of such indemnified party unless (i) the
indemnifying party and the indemnified party shall have mutually agreed to the
retention of such counsel or (ii) the named parties to any such proceeding
(including any impleaded parties) include both the indemnifying party and the
indemnified party and representation of both parties by the same counsel would
be inappropriate due to actual or potential differing interests between them. It
is understood that the indemnifying party shall not, in respect of the legal
expenses of any indemnified party in connection with any proceeding or related
proceedings in the same jurisdiction, be liable for the fees and expenses of
more than one separate firm (in addition to any local counsel) for all such
indemnified parties and that all such fees and expenses shall be reimbursed as
they are incurred. Such firm shall be designated in writing by, in the case of
parties indemnified pursuant to Section 6(a), the Holders of a majority (with
Holders of Debentures deemed to be the Holders, for purposes of determining such
majority, of the number

                                       17
<Page>

of shares of Underlying Common Stock into which such Debentures are or would be
convertible as of the date on which such designation is made) of the Registrable
Securities covered by the Registration Statement held by Holders that are
indemnified parties pursuant to Section 6(a) and, in the case of parties
indemnified pursuant to Section 6(b), the Company. The indemnifying party shall
not be liable for any settlement of any proceeding effected without its written
consent, but if settled with such consent or if there be a final judgment for
the plaintiff, the indemnifying party agrees to indemnify the indemnified party
from and against any loss or liability by reason of such settlement or judgment.
Notwithstanding the foregoing sentence, if at any time an indemnified party
shall have requested an indemnifying party to reimburse the indemnified party
for fees and expenses of counsel as contemplated by the second and third
sentences of this paragraph, the indemnifying party agrees that it shall be
liable for any settlement of any proceeding effected without its written consent
if (i) such settlement is entered into more than 30 days after receipt by such
indemnifying party of the aforesaid request and (ii) such indemnifying party
shall not have reimbursed the indemnified party in accordance with such request
prior to the date of such settlement. No indemnifying party shall, without the
prior written consent of the indemnified party, effect any settlement of any
pending or threatened proceeding 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 claims that are the subject matter
of such proceeding.

          (d) CONTRIBUTION. To the extent that the indemnification provided for
in Section 6(a) or 6(b) is unavailable to an indemnified party or insufficient
in respect of any losses, claims, damages or liabilities referred to therein,
then each indemnifying party under such paragraph, in lieu of indemnifying such
indemnified party thereunder, shall contribute to the amount paid or payable by
such indemnified party as a result of such losses, claims, damages or
liabilities (i) in such proportion as is appropriate to reflect the relative
benefits received by the indemnifying party or parties on the one hand and the
indemnified party or parties on the other hand or (ii) if the allocation
provided by clause (i) above is not permitted by applicable law, in such
proportion as is appropriate to reflect not only the relative benefits referred
to in clause (i) above but also the relative fault of the indemnifying party or
parties on the one hand and of the indemnified party or parties on the other
hand in connection with the statements or omissions that resulted in such
losses, claims, damages or liabilities, as well as any other relevant equitable
considerations. The relative benefits received by the Company shall be deemed to
be equal to the total net proceeds from the initial placement pursuant to the
Purchase Agreement (before deducting expenses) of the Registrable Securities to
which such losses, claims, damages or liabilities relate. The relative benefits
received by any Holder shall be deemed to be equal to the value of receiving
Registrable Securities that are registered under the Securities Act. The
relative fault of the Holders on the one hand and the Company on the other hand
shall be determined by reference to, among other things, whether the untrue or
alleged untrue statement of a material fact or the omission or alleged omission
to state a material fact relates to information supplied by the Holders or by
the Company, and the parties' relative intent, knowledge, access to information
and opportunity to

                                       18
<Page>

correct or prevent such statement or omission. The Holders' respective
obligations to contribute pursuant to this paragraph 6 are several in proportion
to the respective number of Registrable Securities they have sold pursuant to a
Registration Statement, and not joint.

         The parties hereto agree that it would not be just and equitable if
contribution pursuant to this Section 6(d) were determined by PRO RATA
allocation or by any other method of allocation that does not take into account
the equitable considerations referred to in the immediately preceding paragraph.
The amount paid or payable by an indemnified party as a result of the losses,
claims, damages or liabilities referred to in the immediately preceding
paragraph shall be deemed to include, subject to the limitations set forth
above, any legal or other expenses reasonably incurred by such indemnified party
in connection with investigating or defending any such action or claim.
Notwithstanding this Section 6, no indemnifying party that is a selling Holder
shall be required to contribute any amount in excess of the amount by which the
total price at which the Registrable Securities sold by it and distributed to
the public were offered to the public exceeds the amount of any damages that
such indemnifying party 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.

          (e) The remedies provided for in this Section 6 are not exclusive and
shall not limit any rights or remedies which may otherwise be available to an
indemnified party at law or in equity, hereunder, under the Purchase Agreement
or otherwise.

          (f) The indemnity and contribution provisions contained in this
Section 6 shall remain operative and in full force and effect regardless of (i)
any termination of this Agreement, (ii) any investigation made by or on behalf
of any Holder, any person controlling any Holder or any affiliate of any Holder
or by or on behalf of the Company, its officers or directors or any person
controlling the Company and (iii) the sale of any Registrable Securities by any
Holder.

         SECTION 7. INFORMATION REQUIREMENTS. The Company covenants that, if at
any time before the end of the Effectiveness Period the Company is not subject
to the reporting requirements of the Exchange Act, it will cooperate with any
Holder and take such further reasonable action as any Holder may reasonably
request in writing (including, without limitation, making such reasonable
representations as any such Holder may reasonably request), all to the extent
required from time to time to enable such Holder to sell Registrable Securities
without registration under the Securities Act within the limitation of the
exemptions provided by Rule 144 and Rule 144A under the Securities Act and
customarily taken in connection with sales pursuant to such exemptions. Upon the
written request of any Holder, the Company shall deliver to such Holder a
written statement as to whether it has complied with such filing requirements,
unless such a statement has been included in the Company's most recent report
filed pursuant to Section 13 or Section 15(d) of Exchange Act. Notwithstanding
the foregoing, nothing in this

                                       19
<Page>

Section 7 shall be deemed to require the Company to register any of its
securities (other than the Common Stock) under any section of the Exchange Act.

         SECTION 8.  MISCELLANEOUS.

         (a) NO CONFLICTING AGREEMENTS. The Company is not, as of the date
hereof, a party to, nor shall it, on or after the date of this Agreement, enter
into, any agreement with respect to its securities that conflicts with the
rights granted to the Holders in this Agreement. The Company represents and
warrants that the rights granted to the Holders hereunder do not in any way
conflict with the rights granted to the holders of the Company's securities
under any other agreements.

         (b) AMENDMENTS AND WAIVERS. The provisions of this Agreement,
including the provisions of this sentence, may not be amended, modified or
supplemented, and waivers or consents to departures from the provisions hereof
may not be given, unless the Company has obtained the written consent of Holders
of a majority of the then outstanding Underlying Common Stock constituting
Registrable Securities (with Holders of Debentures deemed to be the Holders, for
purposes of this Section, of the number of outstanding shares of Underlying
Common Stock into which such Debentures are or would be convertible as of the
date on which such consent is requested). Notwithstanding the foregoing, a
waiver or consent to depart from the provisions hereof with respect to a matter
that relates exclusively to the rights of Holders whose securities are being
sold pursuant to a Registration Statement and that does not directly or
indirectly affect the rights of other Holders may be given by Holders of at
least a majority of the Registrable Securities being sold by such Holders
pursuant to such Registration Statement; PROVIDED that the provisions of this
sentence may not be amended, modified or supplemented except in accordance with
the provisions of the immediately preceding sentence. Notwithstanding the
foregoing sentence, (i) this Agreement may be amended by written agreement
signed by the Company and the Initial Purchaser, without the consent of the
Holders of Registrable Securities, to cure any ambiguity or to correct or
supplement any provision contained herein that may be defective or inconsistent
with any other provision contained herein, or to make such other provisions in
regard to matters or questions arising under this Agreement that shall not
adversely affect the interests of the Holders of Registrable Securities. Each
Holder of Registrable Securities outstanding at the time of any such amendment,
modification, supplement, waiver or consent or thereafter shall be bound by any
such amendment, modification, supplement, waiver or consent effected pursuant to
this Section 8(b), whether or not any notice, writing or marking indicating such
amendment, modification, supplement, waiver or consent appears on the
Registrable Securities or is delivered to such Holder.

          (c) NOTICES. All notices and other communications provided for or
permitted hereunder shall be made in writing by hand delivery, by telecopier, by
courier guaranteeing overnight delivery or by first-class mail, return receipt
requested, and shall be deemed given (i) when made, if made by hand delivery,
(ii) upon confirmation, if made by telecopier, (iii) one (1) Business Day

                                       20
<Page>

after being deposited with such courier, if made by overnight courier or (iv) on
the date indicated on the notice of receipt, if made by first-class mail, to the
parties as follows:

                   (i) if to a Holder, at the most current address given by such
          Holder to the Company in a Notice and Questionnaire or any amendment
          thereto;

                  (ii)  if to the Company, to:

                        Aon Corporation
                        200 East Randolph Street
                        Chicago, Illinois 60601
                        Attention: General Counsel
                        Telecopy No.: (312) 381-6165

                        and

                        Sidley Austin Brown & Wood LLP
                        787 Seventh Avenue
                        New York, New York 10016
                        Attention: Michael Kohler
                        Telecopy No.: (212) 839-5599

                (iii)   if to the Initial Purchaser, to:

                        Morgan Stanley & Co. Incorporated
                        1585 Broadway
                        New York, New York
                        Attention: Equity Capital Markets
                        Telecopy No.: (212) 761-0538

or to such other address as such person may have furnished to the other persons
identified in this Section 8(c) in writing in accordance herewith.

          (d) APPROVAL OF HOLDERS. Whenever the consent or approval of Holders
of a specified percentage of Registrable Securities is required hereunder,
Registrable Securities held by the Company or its affiliates (as such term is
defined in Rule 405 under the Securities Act) (other than the Initial Purchaser
or subsequent Holders if such subsequent Holders are deemed to be such
affiliates solely by reason of their holdings of such Registrable Securities)
shall not be counted in determining whether such consent or approval was given
by the Holders of such required percentage.

                                       21
<Page>

          (e) SUCCESSORS AND ASSIGNS. Any person who purchases any Registrable
Securities from the Initial Purchaser shall be deemed, for purposes of this
Agreement, to be an assignee of the Initial Purchaser. This Agreement shall
inure to the benefit of and be binding upon the successors and assigns of each
of the parties and shall inure to the benefit of and be binding upon each Holder
of any Registrable Securities, PROVIDED that nothing herein shall be deemed to
permit any assignment, transfer or other disposition of Registrable Securities
in violation of the terms of the Indenture. If any transferee of any Holder
shall acquire Registrable Securities, in any manner, whether by operation of law
or otherwise, such Registrable Securities shall be held subject to all of the
terms of this Agreement, and by taking and holding such Registrable Securities,
such person shall be conclusively deemed to have agreed to be bound by and to
perform all of the terms and provisions of this Agreement and such person shall
be entitled to receive the benefits hereof.

          (f) COUNTERPARTS. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be original and all of which taken together
shall constitute one and the same agreement.

          (g) HEADINGS. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

          (h) GOVERNING LAW.  THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

          (i) SEVERABILITY. If any term provision, covenant or restriction of
this Agreement is held to be invalid, illegal, void or unenforceable, the
remainder of the terms, provisions, covenants and restrictions set forth herein
shall remain in full force and effect and shall in no way be affected, impaired
or invalidated thereby, and the parties hereto shall use their best efforts to
find and employ an alternative means to achieve the same or substantially the
same result as that contemplated by such term, provision, covenant or
restriction, it being intended that all of the rights and privileges of the
parties shall be enforceable to the fullest extent permitted by law.

          (j) ENTIRE AGREEMENT. This Agreement is intended by the parties as a
final expression of their agreement and is intended to be a complete and
exclusive statement of the agreement and understanding of the parties hereto in
respect of the subject matter contained herein and the registration rights
granted by the Company with respect to the Registrable Securities. Except as
provided in the Purchase Agreement, there are no restrictions, promises,
warranties or undertakings, other than those set forth or referred to herein,
with respect to the registration rights granted by the Company with respect to
the Registrable Securities. This Agreement supersedes all prior agreements and
undertakings among the parties with respect to such registration rights. No
party hereto shall have any rights, duties or obligations other than those
specifically set forth in this Agreement. In no event will such methods of
distribution take the form of an underwritten offering of the Registrable
Securities without the prior agreement of the Company.

                                       22
<Page>

          (k) TERMINATION. This Agreement and the obligations of the parties
hereunder shall terminate upon the end of the Effectiveness Period, except for
any liabilities or obligations under Section 4, 5 or 6 hereof and the
obligations to make payments of and provide for liquidated damages under Section
2(e) hereof to the extent such damages accrue prior to the end of the
Effectiveness Period, each of which shall remain in effect in accordance with
its terms.

                                       23
<Page>

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

                                       Aon CORPORATION


                                       By:  /s/ Patrick G. Ryan
                                           -------------------------------------
                                           Name:  Patrick G. Ryan
                                           Title: Chairman and Chief Executive
                                                   Officer


Confirmed and accepted as of the date first above written:

MORGAN STANLEY & CO. INCORPORATED


By:  /s/ Trevor R. Burgess
   -------------------------------------
     Name:  Trevor R. Burgess
     Title: Vice President