Used this one a long time ago but a friend just reminded me about it.  This little tool will retrieve your product keys for software like Windows and Office.  I know I've lost the little piece of paper with the key on it before and got real pissed when I need to install that piece of software again!  Or the time I get all preparred to spend my whole weekend reinstalling Windows and everything else and can't find all the numbers!  This little dude can come in handy.  Magical Jelly Bean Keyfinder