Official Method by Microsoft – more information here.
First Method
- Lauch Windows Task Manager.
- End wgatray.exe process in Task Manager.
- Restart Windows XP in Safe Mode.
- Delete WgaTray.exe from c:\Windows\System32.
- Delete WgaTray.exe from c:\Windows\System32\dllcache.
- Lauch RegEdit.
- Browse to the following location:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\Notify - Delete the folder ‘WgaLogon’ and all its contents
- Reboot Windows XP.
Note: With this method, you may be prompted to install WGA Notifications again which can still be unselected.