The main reason you might want change the Windows XP product key is because your key is pirated or otherwise incorrect but you don't want to reinstall Windows XP to activate your new legal product key.
Note: I created this step by step guide in addition to my original How to Change the Windows XP Product Key Code guide. There are several very specific steps in this process, many of which involve editing the Windows Registry, so this visual tutorial should help clear up any confusion.
Changing your Windows XP product key should take you less than 15 minutes.
The first thing you need to do is click on Start and then Run....