Guaranteed Excel Decryptor Description:

It is a command-line utility which allows you to decrypt Microsoft Excel 97/2000 (and Excel XP in default, 40-bit mode) files with password for opening. Any file, encrypted with ANY password (no matter what length of the password is or what language or symbols used, etc) can be decrypted with guarantee.It usually takes several days. This software supports several computers - the more clients version you have, the faster is the decryption. This is a command-line utility.
Look at http://www.password-crackers.com/crack/guaexcel.html
for more info.