findout out which product key

[memory]

This may be a stupid question but how do I find out which product key I used for the Windows XP I have installed? I have 2 or 3 different Windows cd's and can't remember which one I used. Does it say somewhere on the computer? Or do I have to call Microsoft?

Sorry about the title. I would change but there don't seem to be a way to change it.

 

[leSHok]

isnt there a sticker on the pc or under the pc somewhere that has a code. id look but im too lazy.

 

[kobaj]

Magic jellybean windows key finder.