Remove Windows Genuine Advantage Validation

1) Run regedit from the command prompt

2) Search for the key "WGA" without the quotes

3) Delete all keys related to WGA

4) Restart your PC with Knoppix or Linux bootable disc and go to system folder c:Windows\system32

5) Delete the following files - wgatray.exe, spmsg.dll, wgalogon.dll, LegitCheckControl.dll

6) Reboot your pc

That will remove the genuine validation and the nag screen as well.