Your condition, dj, is due to improperly installed/removed video drivers. <duck>
Go to
Guru3 and use one of the removal tools after you have removed the drivers in Add/Remove Programs. I usually download the new drivers (do not install yet) before rebooting. Don't install by using "New Hardware Found..." Please read all of the Readme information.
If you want to do this easily, consider the following. Right now, Windows Update is providing nVidia drivers 4.5.2.3 and they work well. Just remove your drivers, use one of the removal programs (tools) at the link above, reboot, and go to Windows Update. You will be happy.
The latest drivers do not always provide the fastest video. Get a baseline at
PC Pitstop for comparisons in the future.