Change Product Key (Windows XP)

From ben.goodacre.name/tstage

If Windows Update or Genuine check is complaining about an non-genuine install of Windows and you have a legit key it can be changed by following these steps:

1. Change one of the values in this key to deactivate Windows: HKLM\Software\Microsoft\WindowsNT\CurrentVersion\WPAEvents
2. Run this command-line to force a reactivation: %systemroot%\system32\oobe\msoobe.exe /a
3. Choose the option: Yes, I want to telephone a customer service representative to activate Windows
4. Click: Change Product key, after which the programme can be closed - the wizard does not have to finish.

You may need to reboot before you can start using Windows Update etc.

[edit] See Also

KB328874

Registry