RockXP allows you to retrieve your XP product key that you used when you installed Windows XP, as well as keys for other Microsoft products. This can come very handy if you need to reinstall but have misplaced or lost the CD cover with the serial sticker. In addition, the program also lets you save the product activation to a file, and enables you to recover usernames and passwords contained in the Windows Secure Storage.
RockXP download and review - recover XP activation code from SnapFiles