UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

(Amendment No.  )

Filed by the Registrant   o

Filed by a Party other than the Registrant   x

Check the appropriate box:

o           Preliminary Proxy Statement

¨           Confidential, for Use of the Commission Only (as permitted by Rule14a-6(e)(2))

¨           Definitive Proxy Statement

x          Definitive Additional Materials

o           Soliciting Material Under Rule 14a-12

ADAPTEC, INC.

(Name of Registrant as Specified in Its Charter)

STEEL PARTNERS II, L.P.

STEEL PARTNERS HOLDINGS L.P.

STEEL PARTNERS LLC

STEEL PARTNERS II GP LLC

WARREN G. LICHTENSTEIN

JACK L. HOWARD

JOHN J. QUICKE

(Name of Persons(s) Filing Proxy Statement, if Other Than the Registrant)

Payment of Filing Fee (Check the appropriate box):

x          No fee required.

¨           Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

(1)           Title of each class of securities to which transaction applies:

(2)           Aggregate number of securities to which transaction applies:

(3) Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (set forth the amount on which the filing fee is calculated and state how it was determined):

(4)           Proposed maximum aggregate value of transaction:

(5)           Total fee paid:

¨           Fee paid previously with preliminary materials:

¨           Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously.  Identify the previous filing by registration statement number, or the form or schedule and the date of its filing.

(1)           Amount previously paid:

(2)           Form, Schedule or Registration Statement No.:

(3)           Filing Party:

(4)           Date Filed:

Steel Partners II, L.P. (“SP II”), together with the other participants named herein, is filing materials contained in this Schedule 14A with the Securities and Exchange Commission (“SEC”) in connection with the solicitation of consents from stockholders of Adaptec, Inc., a Delaware corporation (“Adaptec”), for the removal of two directors, Sundi Sundaresh and Robert Loarie, from the Board of Directors of Adaptec (the “Consent Solicitation”).  SP II has filed a definitive consent statement with the SEC with regard to the Consent Solicitation.

Item 1: Presentation to shareholders: