Here are some commands, tools and links to help determine and/or change your Windows Product Key.
- Run the command: winver
- Control Panel-->System
- ProduKey from NirSoft
- Retrieve my Windows 2000/XP/2003 or Office 2000/XP CD Key tool: Magical Jelly Bean Keyfinder
- Other tool to read Microsoft registry product keys: CD Key Reader
- Tool to determine what hardware "XP activation" detected has changed on your system: http://www.licenturion.com/xp/