Exhibit 10.5.1 Note: Portions of this exhibit indicated by "[*]" are subject to a confidential treatment request, and have been omitted from this exhibit. Complete, unredacted copies of this exhibit have been filed with the Securities and Exchange Commission as part of Expedia's confidential treatment request. July 26, 2001 Richard Bray VP, MSN - US Region Microsoft Corp. One Microsoft Way Redmond, WA 98052-6399 RE MSN/Expedia Carriage and Cross Promotion Agreement dated June 29, 2001 ("Agreement") Expedia Gross Profit per Transaction from December 1, 2000 through June 30, 2001 ("Opening Period") Dear Richard: In accordance with Section 4.4 of the Agreement, the parties agree that the figures below specify the Average Gross Profit to EI per Transaction by transaction type achieved during the first and second quarter of EI's fiscal year 2001, and thus the payment amount per Transaction to be paid by EI to MSN for Transactions occurring during the Opening Period, as further defined in Section 4.8 of the Agreement. - ------------------------------------------------------------------------------------------------------------- * Performance Payment Due Microsoft **Average Gross Profit Payment Amount Due (% of avg. Gross Profit) to EI per Transaction Microsoft per Transaction - ------------------------------------------------------------------------------------------------------------- Air Transactions 30% [*] [*] - ------------------------------------------------------------------------------------------------------------- Car Transactions 25% [*] [*] - ------------------------------------------------------------------------------------------------------------- Merchant Accommodations Transactions 25% [*] [*] - ------------------------------------------------------------------------------------------------------------- Agency Accommodations Transactions 25% [*] [*] - ------------------------------------------------------------------------------------------------------------- * Weighted Average calculated in accordance with Section 4.3(b). ** Determined based on Q1 and Q2 FY01 The parties agree that defined terms in this letter agreement have the same meaning as set forth in the Agreement, except as otherwise provided. The parties have caused this Agreement to be executed by their duly authorized representatives as of the Effective Date. MICROSOFT CORPORATION EXPEDIA, INC. By /s/ Richard Bray By /s/ Gregory S. Stanger ------------------------------ -------------------------------- Name (Print) Richard Bray Name (Print) Gregory Stanger -------------------- ---------------------- Title VP-MSN US Region Title Sr. VP and CFO --------------------------- ----------------------------- ------------------------------------------------ [*] - CERTAIN INFORMATION ON THIS PAGE HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS ------------------------------------------------