99% of the time this is caused by not having your video card's drivers installed. because they where using the stock video card drivers from the OS.
I would try a reinstall on the video drivers following the correct way to remove the drivers. Check out the boards over at
http://www.guru3d.com/files/
I used the save version when I had my Ti4600 and did not have a problem. You may also want to check his DirectX version is out but I would stick with the latest 8's until you fix this problem.
Good luck and let us know how you make out.