As part of my recent migration to a new PC, I needed to find the product keys for various programs I was planning to reinstall. Easier said than done. (When, when will I organize this disaster area of a home office?)
Fortunately, I found a sweet utility that saved me hours of rummaging through boxes. Magical Jelly Bean's Keyfinder quickly and efficiently finds the product keys for installed programs, then lets you print them for safekeeping.
It's compatible with all versions of Windows and can dig up the keys for your operating system, Office apps, and various other programs. On my machine it found keys not just for Windows XP and Office 2003, but also for Command and Conquer: Generals (best RTS game ever, if you want my opinion).
Keyfinder is fast, free, and incredibly handy. It doesn't even require installation. I recommend it not just for those migrating to new PCs, but for anyone who wants to keep a hardcopy of important product keys.