I don't know anything about Vista, but I'm fishing to try to give you some ideas to try.

Can you change all the display settings yourself to get them where they were before the game install?
Have you tried uninstalling the new graphics driver?
Have you manually run an anti-virus scan to be sure something isn't active there?
Have you done a disk cleanup to get rid of temporary files and clean out the recycle bin?
Have you tried several restore points, especially the earliest ones available and then initiated the automatic updates to your system (if any)?
Have you contacted Microsoft support to see if they can offer any help? Sometimes support websites have FAQ's which might shed some light on your particular problem.

Wish I could help. I know how frustrating this can be...