Could you please be a little more explict as to what is hapening and why you think you need to validate?
Do you receive an error message ot dialog box saying your copy of Windows is not valid?
What were you doing when the error message/dialog box appeared?
What does it actually say?
In order to provide a ready resource for our customers to troubleshoot validation problems we have provided the following diagnostic site:
http://www.microsoft.com/genuine/diag/
By following the directions on this site you may be able to resolve this issue. If this still fails please provide us with the diagnostics information from the WGA Diag Tool located here:
http://go.microsoft.com/fwlink/?linkid=52012
By using the “copy” button you can paste the information in its entirety to the forum.
Note: Never post Product Keys to the internet or these forums
Hth
dave