If the link that Carey provided does not resolve the issue, download and run the Genuine Diagnostics tool (MGADiag.exe) at this link http://go.microsoft.com/fwlink/?linkid=52012. Click "Continue", click the "Copy" button then “Paste” the report into a reply message in this thread.
If you do not have access to the Start Button:
1) Login to Vista and click the option that brings up Internet Explorer.
2) Type: http://go.microsoft.com/fwlink/?linkid=52012 into the browser address bar.
3) A window will come up asking if you want to “Run” or “Save”, Select “Run”
4) When the program runs, click the “Continue” button, then click the “Copy” button.
5) Return to this thread http://social.microsoft.com/Forums/en-US/genuinevista/thread/a66bc290-e589-4cd9-9438-3448983b9a2d.
6) In a reply post, paste the Diagnostic Report.
Thank you,
Darin MS