Try manually uninstalling all of the drivers for all of your devices, doing a system repair (boot from the CD and at the screen that shows you what old versions it found on your HD, do an 'r').
Once you're done with that, re-install the latest drivers for everything (get new ones from the net).
That should solve it.
Don't forget to do Windows updates when you're done.
i tried that too, worked 4 about an hour. Now it wont even boot. Getting error beeps, 3 long, and red led lights on motherboard are showing up, telling me according to the book, bad board or cpu. The computer is apart now, and going to move the 4 hard drives to another machine for my server. Tried clearing cmos too. Hmmmm, maybe having the computer on 24-7 for 2 years made it die.