If your going to reinstall Windows XP then you’ll need to locate your product key, this is also known as the CD key. Normally this product key is on a sticker on your computer or located with the manual that came with Windows XP computer. If you’ve lost your hard copy of the product key, don’t worry to much as it’s located in the registry but it’s encrypted and not in a readable format , making finding it very difficult.
1. Download a suitable free program that will locate the CD key for you ( see http://pcsupport.about.com/od/productkeysactivation/tp/topkeyfinder.htm )
2. Install and run the chosen program, the product key should be formatted like xxxxx-xxxxx-xxxxx-xxxxx-xxxxx – five sets of five letters and numbers. Locate this and make a note of it. Make sure you write it down correctly if its wrong, you will have major issues.
3. You can now re install Windows as you have a note of your product key. Should you need it during install or activation.