I just read the post of mpjesse. This is very encouraging because my son managed to lose my disc and packaging of my copy of windows xp pro. However, I don't see the name of the programme or where to get it. Could mpjesse or anyone else give me this info please it would be much appreciated and save me a world of trouble.
If you're looking for the key to reinstall existing, still installed and legitimate copy of XP, Google for MagicalJellyBean and use that to fish out and decrypt the key from your system. It won't help you much because it will only work with the CD you use to reinstall but you could telephone Microsoft Activation help desk and ask them to change the Product Key.
However, if you're trying to generate a new key to legitimise a system, ex_bubblehead's post still applies.