Yhis is what causes the problem:

WGA Validation Tool (KB892130) and WGA Notifications (KB905474) (from auto-updates) install the filesLegitCheckControl.dll, WgaLogon.dll and WgaTray.exe.to your system.



This is an easy fix (there is also a manual one):

Apply Hotfix on this (the 007) page. It will install KB905474 WGAnotify with 3 patched WGA files namely LegitCheckControl.dll, WgaLogon.dll and WgaTray.exe. If you run into trouble or it fails:



Alternative:

By using System Restore to restore the PC to a previous restore point that WGA Notifications hasn’t kicked in, and then carefully stop KB905474 from been applied to the system.

To use System Restore, go to Start -> All Programs -> Accessories -> System Tools -> System Restore.

Note: Again, you may be prompted again to install WGA Notification, so it must be bypassed.
'
Once you've done his reset automatic update to 'notify me first' so you can monitor what Microsoft is installing.ie KB905474

                             Ant.