UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  -------------

                                  SCHEDULE 13D
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
            TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO
                                  RULE 13d-2(a)

                    Under the Securities Exchange Act of 1934
                                (Amendment No.5)*



                             Fair Isaac Corporation
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                                (Name of Issuer)

                                  Common Stock
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                         (Title of Class of Securities)

                                    303250104
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                                 (CUSIP Number)

                         Sandell Asset Management Corp.
                               40 West 57th Street
                                   26th Floor
                               New York, NY 10019
                   Attention: Richard Gashler, General Counsel
                                  212-603-5700

                                 With a Copy to:
                              Marc Weingarten, Esq.
                            Schulte Roth & Zabel LLP
                                919 Third Avenue
                               New York, NY 10019
                                  212-756-2000
- --------------------------------------------------------------------------------
(Name, Address and Telephone Number of Person Authorized to Receive Notices and
                                 Communications)

                               September 16, 2009
                               ------------------
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box
[ ].

Note: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 13d-7 for other parties
to whom copies are to be sent.

                          (Continued on following pages)
                               (Page 1 of 8 Pages)

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* The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page. The information required on the
remainder of this cover page shall not be deemed to be "filed" for the purpose
of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise
subject to the liabilities of that section of the Act but shall be subject to
all other provisions of the Act (however, see the Notes).

- ---------------------------- ---------------------------- CUSIP No. 303250104 SCHEDULE 13D Page 2 of 8 Pages - ---------------------------- ---------------------------- - ------------- ----------------------------------------------------------------- 1 NAME OF REPORTING PERSON Castlerigg Master Investments Ltd. - ------------- ----------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_| (b) |_| - ------------- ----------------------------------------------------------------- 3 SEC USE ONLY - ------------- ----------------------------------------------------------------- 4 SOURCE OF FUNDS WC - ------------- ----------------------------------------------------------------- 5 CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) |_| - ------------- ----------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION British Virgin Islands - ------------- ----------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER SHARES 0 ----------- ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER OWNED 2,211,839 ----------- ----------------------------------------------------- BY EACH 9 SOLE DISPOSITIVE POWER REPORTING 0 ----------- ----------------------------------------------------- PERSON 10 SHARED DISPOSITIVE POWER 2,211,839 WITH - ------------- ----------- ----------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,211,839 - ------------- ----------------------------------------------------------------- 12 CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - ------------- ----------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11 4.5% - ------------- ----------------------------------------------------------------- 14 TYPE OF REPORTING PERSON CO - ------------- -----------------------------------------------------------------

- ---------------------------- ---------------------------- CUSIP No. 303250104 SCHEDULE 13D Page 3 of 8 Pages - ---------------------------- ---------------------------- - ------------- ----------------------------------------------------------------- 1 NAME OF REPORTING PERSON Sandell Asset Management Corp. - ------------- ----------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_| (b) |_| - ------------- ----------------------------------------------------------------- 3 SEC USE ONLY - ------------- ----------------------------------------------------------------- 4 SOURCE OF FUNDS AF - ------------- ----------------------------------------------------------------- 5 CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) |_| - ------------- ----------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands - ------------- ----------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER SHARES 0 ----------- ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER OWNED 2,211,839 ----------- ----------------------------------------------------- BY EACH 9 SOLE DISPOSITIVE POWER REPORTING 0 ----------- ----------------------------------------------------- PERSON 10 SHARED DISPOSITIVE POWER 2,211,839 WITH - ------------- ----------- ----------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,211,839 - ------------- ----------------------------------------------------------------- 12 CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - ------------- ----------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11 4.5% - ------------- ----------------------------------------------------------------- 14 TYPE OF REPORTING PERSON CO - ------------- -----------------------------------------------------------------

- ---------------------------- ---------------------------- CUSIP No. 303250104 SCHEDULE 13D Page 4 of 8 Pages - ---------------------------- ---------------------------- - ------------- ----------------------------------------------------------------- 1 NAME OF REPORTING PERSON Castlerigg International Limited - ------------- ----------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_| (b) |_| - ------------- ----------------------------------------------------------------- 3 SEC USE ONLY - ------------- ----------------------------------------------------------------- 4 SOURCE OF FUNDS AF - ------------- ----------------------------------------------------------------- 5 CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) |_| - ------------- ----------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION British Virgin Islands - ------------- ----------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER SHARES 0 ----------- ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER OWNED 2,211,839 ----------- ----------------------------------------------------- BY EACH 9 SOLE DISPOSITIVE POWER REPORTING 0 ----------- ----------------------------------------------------- PERSON 10 SHARED DISPOSITIVE POWER 2,211,839 WITH - ------------- ----------- ----------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,211,839 - ------------- ----------------------------------------------------------------- 12 CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - ------------- ----------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11 4.5% - ------------- ----------------------------------------------------------------- 14 TYPE OF REPORTING PERSON CO - ------------- -----------------------------------------------------------------

- ---------------------------- ---------------------------- CUSIP No. 303250104 SCHEDULE 13D Page 5 of 8 Pages - ---------------------------- ---------------------------- - ------------- ----------------------------------------------------------------- 1 NAME OF REPORTING PERSON Castlerigg International Holdings Limited - ------------- ----------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_| (b) |_| - ------------- ----------------------------------------------------------------- 3 SEC USE ONLY - ------------- ----------------------------------------------------------------- 4 SOURCE OF FUNDS AF - ------------- ----------------------------------------------------------------- 5 CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) |_| - ------------- ----------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION British Virgin Islands - ------------- ----------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER SHARES 0 ----------- ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER OWNED 2,211,839 ----------- ----------------------------------------------------- BY EACH 9 SOLE DISPOSITIVE POWER REPORTING 0 ----------- ----------------------------------------------------- PERSON 10 SHARED DISPOSITIVE POWER 2,211,839 WITH - ------------- ----------- ----------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,211,839 - ------------- ----------------------------------------------------------------- 12 CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - ------------- ----------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11 4.5% - ------------- ----------------------------------------------------------------- 14 TYPE OF REPORTING PERSON CO - ------------- -----------------------------------------------------------------

- ---------------------------- ---------------------------- CUSIP No. 303250104 SCHEDULE 13D Page 6 of 8 Pages - ---------------------------- ---------------------------- - ------------- ----------------------------------------------------------------- 1 NAME OF REPORTING PERSON Thomas E. Sandell - ------------- ----------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_| (b) |_| - ------------- ----------------------------------------------------------------- 3 SEC USE ONLY - ------------- ----------------------------------------------------------------- 4 SOURCE OF FUNDS AF - ------------- ----------------------------------------------------------------- 5 CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) |_| - ------------- ----------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Sweden - ------------- ----------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER SHARES 0 ----------- ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER OWNED 2,211,839 ----------- ----------------------------------------------------- BY EACH 9 SOLE DISPOSITIVE POWER REPORTING 0 ----------- ----------------------------------------------------- PERSON 10 SHARED DISPOSITIVE POWER 2,211,839 WITH - ------------- ----------- ----------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,211,839 - ------------- ----------------------------------------------------------------- 12 CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - ------------- ----------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11 4.5% - ------------- ----------------------------------------------------------------- 14 TYPE OF REPORTING PERSON IN - ------------- -----------------------------------------------------------------

- ---------------------------- ---------------------------- CUSIP No. 303250104 SCHEDULE 13D Page 7 of 8 Pages - ---------------------------- ---------------------------- The Schedule 13D filed on June 29, 2007, as amended by Amendment No. 1 filed on October 15, 2007, Amendment No. 2 filed on December 11, 2007, Amendment No. 3 filed on December 8, 2008, and Amendment No. 4 filed on July 29, 2009 (the "Schedule 13D") by the Reporting Persons (as defined below), relating to the common stock, par value $0.01 per share (the "Common Stock"), of Fair Isaac Corporation, a Delaware corporation (the "Issuer"), is hereby amended as set forth below by this Amendment No. 5 to the Schedule 13D. This Amendment No. 5 also constitutes an "exit filing" for the Reporting Persons, who do not intend to file any further amendments to the Schedule 13D. Except as set forth herein, the Schedule 13D is unmodified. ITEM 5. INTEREST IN SECURITIES OF THE ISSUER Paragraphs (a),(c)and (e) of Item 5 of the Schedule 13D are hereby amended and restated as follows: (a) Each of Castlerigg Master Investments, SAMC, Castlerigg International, Castlerigg Holdings and Sandell may be deemed to beneficially own the 2,211,839 shares of Common Stock held by Castlerigg Master Investments, representing approximately 4.5% of the outstanding shares of Common Stock. The Reporting Persons may be deemed to be a "group," which "group" may be deemed to beneficially own an aggregate of 2,211,839 shares of Common Stock, representing approximately 4.5% of the outstanding shares of Common Stock. The percentages used herein are based upon the 48,855,019 shares of Common Stock reported to be outstanding as of July 31, 2009 by the Issuer in its report on Form 10-Q for the quarterly period ended June 30, 2009, filed with the Securities and Exchange Commission on August 6, 2009. (c) Information concerning transactions in the shares of Common Stock effected by the Reporting Persons since the filing of Amendment No. 4 is set forth on Appendix I hereto and is incorporated herein by reference. Unless otherwise indicated, all of such transactions were effected in the open market. (e) The Reporting Persons ceased to be the beneficial owners of more than 5% of the shares of Common Stock on September 16, 2009.

- ---------------------------- ---------------------------- CUSIP No. 303250104 SCHEDULE 13D Page 8 of 8 Pages - ---------------------------- ---------------------------- Signature After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. Dated: September 18, 2009 CASTLERIGG MASTER INVESTMENTS LTD. By: Sandell Asset Management Corp., as investment manager By: /s/ Thomas E. Sandell --------------------- Thomas E. Sandell, Chief Executive Officer SANDELL ASSET MANAGEMENT CORP. By: /s/ Thomas E. Sandell --------------------- Thomas E. Sandell, Chief Executive Officer CASTLERIGG INTERNATIONAL LIMITED By: Sandell Asset Management Corp., as investment manager By: /s/ Thomas E. Sandell --------------------- Thomas E. Sandell, Chief Executive Officer CASTLERIGG INTERNATIONAL HOLDINGS LIMITED By: Sandell Asset Management Corp., as investment manager By: /s/ Thomas E. Sandell --------------------- Thomas E. Sandell, Chief Executive Officer /s/ Thomas E. Sandell --------------------- Thomas E. Sandell

APPENDIX I TRANSACTIONS EFFECTED SINCE THE FILING OF THE MOST RECENT AMENDMENT TO THE SCHEDULE 13D Castlerigg Master Investments Date Amount of shares purchased/(sold) Price per share (net of commission) 09/11/09 (78,000) $22.23 09/14/09 (139,237) 22.01 09/15/09 (165,900) 21.95 09/16/09 (96,992) 22.06 9/17/09 (182,032) 22.16