CREDIT SUISSE SECURITIES (USA) LLC CREDIT SUISSE AG Eleven Madison Avenue New York, NY 10010 MORGAN STANLEY SENIOR FUNDING, INC. 1585 Broadway New York, NY 10036

Borrower:

Aon Corporation, a Delaware corporation (the “Borrower”).

Transactions:

The Borrower intends to acquire all of the equity interests of Hewitt Associates, Inc. (the “Company”) pursuant to an agreement and plan of merger (the “Merger Agreement”) to be entered into among the Borrower, a newly-formed wholly-owned subsidiary of the Borrower (“Merger Sub”), a second newly formed, wholly-owned subsidiary of the Borrower (“Merger LLC”) and the Company. Pursuant to the Merger Agreement (a) Merger Sub will be merged with and into the Company, with the Company surviving as a wholly-owned subsidiary of the Borrower (the “Merger”), with the equity holders of the Company receiving an aggregate amount of approximately $2.45 billion in cash (the “Merger Cash Consideration”) and approximately 64 million shares of common stock of the Borrower (the “Merger Equity Consideration”, and together with the Merger Cash Consideration, the “Merger Consideration”), (b) immediately following the completion of the Merger, the surviving corporation in the Merger will be merged with and into Merger LLC, with Merger LLC surviving as a wholly-owned subsidiary of Borrower (the “Subsequent Merger”), (c) the Borrower will obtain the three-year term loan described below under the caption “Term Facility”, (d) the Borrower will (i) issue up to $1.5 billion in aggregate principal amount of its senior unsecured notes (the “Notes”) in a public offering or in a Rule 144A or other private placement and (ii) to the extent the Borrower is unable to issue the Notes on or prior to the date the Merger is consummated, borrow up to $1.5 billion in aggregate principal amount of senior increasing rate loans (the “Bridge Loans”) under the new senior credit facility (the “Bridge Facility”) described in Exhibit B to the Commitment Letter, (e) certain of the existing indebtedness of the Company and its subsidiaries outstanding as of the Closing Date (as defined below) (the “Existing Debt”) shall be repaid and (f) fees and expenses incurred in connection with the foregoing in an aggregate amount not to exceed $50 million (the “Transaction Costs”) will be paid. The transactions described in this paragraph are collectively referred to herein as the “Transactions”. The “Closing Date”

shall mean the date on which the Merger is consummated and all the conditions precedent to closing under the Facilities have been satisfied or waived.

Sources and Uses:

The approximate sources and uses of the funds necessary to consummate the Transactions are set forth in Exhibit C to the Commitment Letter (the “Commitment Letter”) to which this Term Sheet is attached.

Agent:

Credit Suisse AG, acting through one or more of its branches or affiliates (“CS”), will act as sole administrative agent (in such capacity, the “Agent”) for a syndicate of banks, financial institutions and other institutional lenders (together with CS, the “Lenders”), and will perform the duties customarily associated with such role.

Joint Bookrunner and Joint Lead Arranger:

Credit Suisse Securities (USA) LLC and Morgan Stanley Senior Funding, Inc. will act as joint bookrunners and joint lead arrangers for the Term Facility described below (collectively, in such capacities, the “Arrangers”), and will perform the duties customarily associated with such roles.

Syndication Agent:

Morgan Stanley Senior Funding, Inc. (in such capacity, the “Syndication Agent”).

Documentation Agent:

One or more financial institutions reasonably acceptable to the Borrower and the Arrangers (collectively in such capacity, the “Documentation Agent”).

Term Facility:

A three-year senior unsecured term loan facility in an aggregate principal amount of up to $1 billion (the “Term Facility” and the loans made pursuant thereto, the “Term Loans”).

Purpose:

The proceeds of the Term Facility will be used by the Borrower, on the Closing Date, together with the proceeds of the Notes or the Bridge Loans, solely (a) to pay a portion of the Merger Cash Consideration, (b) to refinance certain of the Existing Debt and (c) to pay the Transaction Costs.

Availability:

The full amount of the Term Facility must be drawn in a single drawing on the Closing Date. Amounts borrowed under the Term Facility that are repaid or prepaid may not be reborrowed.

Interest Rates and Fees:

As set forth on Annex A-I hereto.

Default Rate:

At the option of the Required Lenders (to be defined)

(or automatically, in the case of a bankruptcy Event of Default), the applicable rate plus 2.00%.

Final Maturity and Amortization:

The Term Facility will mature on the date that is three years after the Closing Date, and will amortize in an aggregate quarterly amount equal to 2.5% of the original principal amount of the Term Facility with the balance payable on the maturity date of the Term Facility.

Voluntary Prepayments and Reductions in Commitments:

Voluntary reductions in the unutilized portion of the commitments under the Term Facility and prepayments of borrowings under the Term Facility will be permitted at any time, in minimum principal amounts to be agreed upon, without premium or penalty, subject to reimbursement of the Lenders’ redeployment costs in the case of a prepayment of Adjusted LIBOR borrowings other than on the last day of the relevant interest period. All voluntary prepayments of the Term Facility will be applied as directed by the Borrower.

Representations and Warranties:

Substantially similar to the Three-Year Credit Agreement, dated December 4, 2009, among the Borrower, Citibank, N.A., as Administrative Agent, and the Lenders party thereto as in effect on the Signing Date (the “Existing Credit Agreement”) (subject to materiality thresholds and exceptions to be mutually agreed between the Arrangers and the Borrower), and shall include: corporate status; legal, valid and binding documentation; government consents; accuracy of financial statements, confidential information memorandum and other information; no Borrower Material Adverse Change or Company Material Adverse Change; absence of undisclosed liabilities, litigation and investigations; no violation of, or conflicts with, agreements or instruments; compliance with laws (including PATRIOT Act, ERISA, margin regulations, environmental laws, laws applicable to sanctioned persons and the Foreign Corrupt Practices Act); payment of taxes; ownership of properties; Investment Company Act; solvency; environmental and other regulatory matters; no default; and insurance and insurance licenses; and treatment as senior debt under all subordinated debt and as sole designated senior debt thereunder (other than the Bridge Facility).

Conditions Precedent to Effectiveness:

Limited to (i) execution and delivery of definitive documentation with respect to the Term Facility consistent with the terms set forth in the Commitment Letter and otherwise mutually agreed by the Borrower

and the Arrangers (the “Term Facility Documentation”), (ii) delivery of customary legal opinions, secretary’s certificates, corporate organizational documents, good standing certificates and resolutions of the Borrower (in each case in customary form), (iii) payment of fees and expenses required to be paid on or prior to the date of effectiveness of the Term Facility Documentation (the “Effective Date) and, with regard to expenses, for which invoices have been presented not less than one business day prior to the Effective Date and (iv) delivery of all documentation and other information requested by the Arrangers at least 5 business days prior to the Effective Date and required by regulatory authorities under applicable “know your customer” and anti-money laundering rules and regulations including, without limitation, the PATRIOT Act; provided that if any such request was received by the Borrower 10 or more business days prior to the Effective Date, the Borrower shall have provided such information or documents at least 5 business days prior to the Effective Date.

Conditions Precedent to Borrowing:

Limited to effectiveness of the Term Facility Documentation; payment of fees and expenses required to be paid on or prior to the Closing Date and, with regard to expenses, for which invoices have been presented not less than one business day prior to the Closing Date; delivery of notice; accuracy of representations and warranties (subject to the Certain Funds Provision) (provided that to the extent any of the foregoing are qualified or subject to “Material Adverse Effect,” the definition thereof shall be Borrower Material Adverse Effect or Company Material Adverse Effect for purposes of satisfying these Conditions Precedent to Borrowing); absence of default; and the applicable conditions precedent set forth in Exhibit D to the Commitment Letter.

Affirmative Covenants:

Substantially similar to the Existing Credit Agreement (subject to materiality thresholds and exceptions to be mutually agreed between the Arrangers and the Borrower), and shall include: maintenance of corporate existence and rights; delivery of consolidated financial statements and other information, including information required under the PATRIOT Act; delivery of notices of default, litigation, ERISA events, change in senior unsecured long term debt rating and material adverse change; maintenance of properties in good working order; maintenance of satisfactory insurance; compliance

with laws; inspection of books and properties; payment of taxes; and conduct of business.

Negative Covenants:

Substantially similar to the Existing Credit Agreement (subject to materiality thresholds and exceptions to be mutually agreed between the Arrangers and the Borrower), and shall include: limitations on dividends on, and redemptions and repurchases of, equity interests; limitations on liens; limitations on subsidiary debt, guarantees and hedging arrangements; limitations on mergers and consolidations; limitations on asset sales; limitations on transactions with affiliates; limitations on changes in fiscal year; limitations on inconsistent agreements; and ERISA.

Financial Covenants:

Subject to definitions substantially similar to the Existing Credit Agreement (provided that additional add-backs shall be permitted to consolidated EBITDA for fees and expenses and other one-time charges related to the Transactions), the following financial covenants, which shall be tested quarterly commencing with the first fiscal quarter ending immediately after the Closing Date: (a) maximum consolidated leverage ratio and (b) minimum interest coverage ratio.

Events of Default:

Substantially similar to the Existing Credit Agreement relating to the Borrower and its subsidiaries (subject to materiality thresholds, grace periods and exceptions to be mutually agreed between the Arrangers and the Borrower), and shall include: nonpayment of principal, interest or other amounts; violation of covenants; incorrectness of representations and warranties in any material respect; cross acceleration to indebtedness other than the Bridge Facility; cross event of default to the Bridge Facility; bankruptcy; material judgments; ERISA events; and Change of Control.

Voting:

Amendments and waivers of the definitive credit documentation will require the approval of Lenders holding more than 50% of the aggregate amount of the loans and commitments under the Term Facility, except that the consent of each Lender shall be required with respect to, among other things, (a) increases in the commitment of such Lender, (b) reductions or forgiveness of principal, interest or fees payable to such Lender, (c) extensions of final maturity or scheduled amortization of the loans or commitments of such Lender or of the date for payment to such Lender of any interest or fees, (d) modifications to any provision requiring pro rata

treatment of the Lenders and (e) modifications to voting requirements or percentages. The Term Facility Documentation will contain customary provisions permitting additional or replacement tranches of Term Loans with the approval of Lenders holding more than 50% of the aggregate amount of the then existing loans and commitments under the Term Facility and each Lender providing such additional or replacement tranche.

Cost and Yield Protection:

Substantially similar to the Existing Credit Agreement, including customary tax gross-up provisions (but excluding gross-up for any withholding or other taxes or liabilities imposed pursuant to the Foreign Account Tax Compliance Act).

Assignments and Participations:

Prior to the Closing Date, the Lenders will be permitted to assign commitments under the Term Facility with the consent of the Borrower, not to be unreasonably withheld or delayed; provided that such consent of the Borrower shall not be required (i) if such assignment is made to another Lender or any affiliate or approved fund of a Lender or (ii) to a Permitted Assignee. From the Closing Date, the Lenders will be permitted to assign loans under the Term Facility with the consent of the Borrower, not to be unreasonably withheld or delayed; provided that such consent of the Borrower (x) shall not be required (i) if such assignment is made to another Lender or an affiliate or approved fund of a Lender, (ii) to a Permitted Assignee or (iii) after the occurrence and during the continuance of a default and (y) shall be deemed to have been given if the Borrower has not responded within five business days of a request for such consent. All assignments will require the consent of the Agent, not to be unreasonably withheld or delayed. Each assignment will be in an amount of an integral multiple of $1,000,000. Assignments will be by novation.

The Lenders will be permitted to sell participations in the Term Loan without restriction. Voting rights of participants shall be limited to matters in respect of (a) increases in commitments of such participant, (b) reductions or forgiveness of principal, interest or fees payable to such participant and (c) extensions of final maturity or scheduled amortization of the loans or commitments in which such participant participates.

Expenses and Indemnification:

The Borrower will indemnify the Arrangers, the

Agent, the Syndication Agent, the Documentation Agent, the Lenders, their respective affiliates, successors and assigns and the officers, directors, employees, agents, advisors, controlling persons and members of each of the foregoing (each, an “Indemnified Person”) and hold them harmless from and against all costs, expenses (including reasonable fees, disbursements and other charges of counsel and liabilities of such Indemnified Person arising out of or relating to any claim or any litigation or other proceeding (regardless of whether such Indemnified Person is a party thereto and regardless of whether such matter is initiated by a third party or by the Borrower, the Company or any of their respective affiliates or equity holders) that relates to the Transactions, including the financing contemplated hereby, the Merger or any transactions in connection therewith; provided that no Indemnified Person will be indemnified for any cost, expense or liability to the extent (x) found in a final, non-appealable judgment of a court of competent jurisdiction to have resulted from (i) the willful misconduct or gross negligence of such Indemnified Person or (ii) a material breach in bad faith by the relevant Indemnified Person of the express contractual obligations of such Indemnified Person under the Term Facility Documentation, or (y) arising out of or in connection with any claim, litigation, investigation or proceeding that does not involve an act or omission of you or any of your affiliates and that is brought by an Indemnified Person against any other Indemnified Person (excluding any claim brought against either Arrangers, the Agent, the Syndication Agent or the Documentation Agent in its capacity as such). In addition, the Borrower shall pay all reasonable out-of-pocket expenses (including, without limitation, fees, disbursements and other charges of counsel (limited, in the case of clause (a), to one counsel for all Indemnified Persons (and, if reasonably necessary, of one regulatory counsel and one local counsel in any relevant jurisdiction for all Indemnified Persons and additional counsel if, in the opinion of an Indemnified Person, representation of all Indemnified Persons by one counsel would be inappropriate due to the existence of an actual or potential conflict of interest)) of (a) the Arrangers, the Agent, the Syndication Agent and the Documentation Agent in connection with the syndication of the Term Facility, the preparation and administration of the definitive documentation, and amendments, modifications and waivers thereto, and (b) the Arrangers, the Agent, the Syndication Agent, the

Documentation Agent and the Lenders for enforcement costs and documentary taxes associated with the Term Facility.

Governing Law and Forum:

New York; provided, however, that the interpretation of the definitions of “Borrower Material Adverse Change” and “Company Material Adverse Change” shall be governed by, and construed in accordance with, the laws of the State of Delaware, regardless of the laws that might otherwise govern under applicable principles of conflicts of laws.

Counsel to Agent and Arrangers:

Davis Polk & Wardwell LLP.

Interest Rates:

At the option of the Borrower, the Term Loan will bear interest at a rate equal to (i) Adjusted LIBOR plus the Applicable Margin or (ii) ABR plus the Applicable Margin.

“Applicable Margin” means the percentage per annum determined in accordance with the pricing grid (the “Term Pricing Grid”) attached hereto as Annex A-I-1.

The Borrower may elect interest periods of 1, 2, 3 or 6 months for Adjusted LIBOR borrowings.

Calculation of interest shall be on the basis of the actual days elapsed in a year of 360 days (or 365 or 366 days, as the case may be, in the case of ABR loans based on the Prime Rate) and interest shall be payable at the end of each interest period and, in any event, at least every three months.

ABR is the Alternate Base Rate, which is the highest of (i) the Agent’s Prime Rate, (ii) the Federal Funds Effective Rate plus ½ of 1.0% and (iii) the one-month Adjusted LIBOR plus 1.0%.

Adjusted LIBOR will at all times include statutory reserves.

Term Undrawn Commitment Fee:

Prior to the date that is 45 days from the Signing Date, 0% per annum, and thereafter 0.375% per annum on the undrawn portion of the commitments in respect of the Term Facility, payable upon the earlier of the termination of the commitments under the Term Facility and the Closing Date, calculated based on the number of days elapsed in a 360 day year.

For the avoidance of doubt, it is understood and agreed that the Term Undrawn Commitment Fee shall replace the Term Ticking Fee (as defined in the Fee Letter) from the Effective Date.