Well, the first thing you should do is cover your bases.
Run your favorite antivirus and antispyware scanners, and perhaps a few online scans for good measure. Trendmicro Housecall, for instance. housecall.trendmicro.com
Then run a chkdsk- Start>Computer>Right click your OS drive (most likely C:)>Properties>Tools tab>Error checking>Check both boxes>Hit "Check now">Reboot
Update your installation of Vista and your drivers (just doing so in the device manager should be adequate)
Boot off of your operating system CD (after ensuring that your computer will look to the CD tray before the hard drive in your SETUP) and Click "repair your computer", select the correct drive, open the Command Prompt, and type in
SFC /Scannow
(optional: Chkdsk C: /r for another chkdsk)
(you can do this within windows, but I like to do it off of the CD for peace of mind)
*note* In my experience, when you boot from the CD, you will have a blank vista background for a few minutes before anything happens. Don't panic!
Run Microsoft Live OneCare SafetyScanner: http://onecare.live.com/site/en-us/center/whatsnew.htm
To clean your computer of junk files, malware, and bad registry entries.
Run CCleaner: www.ccleaner.com
For another level of cleaning junk files and your registry.
If your version of windows is 32-bit, you can get dial-a-fix (Dial-a-Fix: http://wiki.djlizard.net/Dial-a-fix )
I hope one of these solves your problem! I suggest doing them more or less in order, just to be on the safe side.
Good luck! Keep us posted!
--The Comodore