Another alternative suggest that three files are installed Windows XP System Folder for WGA:

\WINDOWS\system32\WgaLogon.dll
\WINDOWS\system32\WgaTray.exe
\WINDOWS\system32\LegitCheckControl.dll

The wgatray.exe process makes the check for genuine windows software. If WgaLogon.dll is denied execution right, that WinLogon is unable to call it to check on Windows validity and display notification package at boot, and since WgaLogon is also responsible for running and maintaining WgaTray.exe, no more tray popups either.

To change and disable the execute bit of WgaLogon.dll:

   1. Turn off Simple File Sharing in Tools -> Folder Options -> View tab.
   2. Right click WgaLogon.dll in Windows Explorer and open the Security Tab.
   3. Click Advanced button.
   4. Uncheck the Inherit box at the bottom.
   5. Click the Copy button.
   6. Click OK.
   7. Go through each listed user/group and remove the “Read & Execute” permission for WgaLogon.dll, leaving the “Read” permission as-is.
   8. Click OK to apply the permission changes.
   9. Close the file properties dialog.
  10. Restart the computer.
  11. Turn “Use simple file sharing” on (optional).