Retreiving lost XP key numbers

Is there anyway to retreive lost XP key numbers? I have an oem xp cd that I purchased for my custom built pc and cannot locate the numbers- thanks in advance!!

http://magicaljellybean.com/keyfinder/

that certificate of authenticity is your proof you purchased windows, I wouldn't lose it

too bad I didn't ask this question before I started the process of re-installing. I have already reformatted the drive and was in the proccess of installing XP when it asked for the numbers, which is when I discovered I could not locate them- dumb on my part i know- hard lesson learned here-

Be sure not to loose them second time around!

Good advice Dachew!