this copy of windows must be activated with microsoft before you can log on.

1. Restart in Safe Mode (F8)
2. Go to /System/32/ and delete wgatray.exe & Go to /dllcache/ if it exists and delete the same .exe If not don't worry about the second.
3. Go to Start => Run => regedit
4. Browse HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\WI… NT\CURRENT VERSION\WINLOGON\Notify
5. Delete WgaLogon folder
6. Reboot.

I guarantee if you do this you won't get any more notices. No need to reinstall Windows or do any of that cumbersome stuff with Microsoft.