Sometimes it becomes necessary to change your XP Product Key if your key is pirated or illegal! How to change the key without reinstalling Windows?
To do that, you need to edit the registry! Type ‘regedit’ in the Run command.
In the registry editor program, go to HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\Current Version\WPAEvents
Click WPAEvents folder and locate OOBETimer on the right pane.
Right click OOBETimer and choose Modify.
Change any one digit to deactivate Windows and click OK.
Once again click Start – Run. Type the following command in the Run box – %systemroot%\system32\oobe\msoobe.exe /a.
When the Windows Product Activation appears choose to activate by telephone. Click Next and choose Change Product Key. Type your new key and click Update.
If you’re taken back to the previous screen, click Remind Me Later.
Lastly restart your PC.