[Allen & Company LLC Letterhead]
November 30, 2007
Shawn McCreight, Chairman
John Colbert, Chief Executive Officer
Guidance Software, Inc.
215 North Marengo Avenue, Second Floor
Pasadena, CA 91101
Dear Shawn and John:
As you may know, I have recently joined Allen & Company LLC in New York. As a result of my new obligation, I believe it will be very difficult for me to continue to reside on the Board of Guidance Software. As a result, I will be resigning by Board position.
In order to accomplish this in an orderly way as possible, I would make the resignation effective as of January 15, 2008.
I have greatly enjoyed my time on the Board and hope there are ways we can continue to work together.
Sincerely,
/s/ George J. Tenet
George J. Tenet