Step 1
Open Start/Run... and type the command:
regedit and click "OK" (or press ENTER).
Go to HKey_Local_Machine\Software\Microsoft\WindowsNT\Current Version\WPAEvents,
on the right double click on "oobetimer" and change at least one digit of this value to deactivate windows.
Click "OK" and close the Registry Editor.
Step 2
Open Start/Run... and type the command:
%systemroot%\system32\oobe\