1. Open the 'Start' menu and type 'cmd' into the 'Search' box.
2. Click on the 'cmd' program that appears at the top of your Start menu.
3. Type in 'slmgr.vbs -ipk x' and press 'Enter,' where 'x' is your correct Windows Vista product key.
4. Type in 'slmgr.vbs -ato' to re-register the correct key, fixing the registration file.
5. Reboot your computer.