**Exhibit 31.2**

**CERTIFICATION OFCHIEF FINANCIAL OFFICER**

**PURSUANT TO SECTION****302 OF THE SARBANES-OXLEY ACT OF 2002**

I, Marshall L. Mohr, certify that:

1.                 I have reviewedthis quarterly report on Form 10-Q of Adaptec, Inc.;

2.                 Based on myknowledge, this report does not contain any untrue statement of a material factor omit to state a material fact necessary to make the statements made, inlight of the circumstances under which such statements were made, notmisleading with respect to the period covered by this report;

3.                 Based on myknowledge, the financial statements, and other financial information includedin this report, fairly present in all material respects the financialcondition, results of operations and cash flows of the registrant as of, andfor, the periods presented in this report;

4.                 The registrant’sother certifying officer and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e)) and internal control over financial reporting (as defined inExchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant andhave:

a)               designed such disclosure controls andprocedures, or caused such disclosure controls and procedures to be designedunder our supervision, to ensure that material information relating to theregistrant, including its consolidated subsidiaries, is made known to us byothers within those entities, particularly during the period in which thisreport is being prepared;

b)              designed suchinternal control over financial reporting, or caused such internal control overfinancial reporting to be designed under our supervision, to provide reasonableassurance regarding the reliability of financial reporting and the preparationof financial statements for external purposes in accordance with generallyaccepted accounting principles;

c)               evaluated the effectiveness of theregistrant’s disclosure controls and procedures and presented in this reportour conclusions about the effectiveness of the disclosure controls andprocedures, as of the end of the period covered by this report based on suchevaluation; and

d)              disclosed in this report any change inthe registrant’s internal control over financial reporting that occurred duringthe registrant’s most recent fiscal quarter (the registrant’s fourth fiscalquarter in the case of an annual report) that has materially affected, or isreasonably likely to materially affect, the registrant’s internal control overfinancial reporting; and

5.                 The registrant’s other certifying officerand I have disclosed, based on our most recent evaluation of internal controlover financial reporting, to the registrant’s auditors and the audit committeeof registrant’s board of directors (or persons performing the equivalentfunction):

a)               all significant deficiencies andmaterial weaknesses in the design or operation of internal control overfinancial reporting which are reasonably likely to adversely affect theregistrant’s ability to record, process, summarize and report financialinformation; and

b)              anyfraud, whether or not material, that involves management or other employees whohave a significant role in the registrant’s internal control over financialreporting.
|                            |   | /s/  MARSHALL L. MOHR |
|----------------------------|--------|----------------------------|
|                       |   | Marshall L. Mohr           |
| Date: August 8,  2005 |   | *Chief Financial Officer*  |

 

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