I just want to add for future readers, that if you want to remove all traces of video drivers, check out
Display Driver Uninstaller. It's for both NVIDIA and ATI/AMD.
You just boot into safe mode, run it, restart, and install new drivers. It turns off
Windows Automatic Driver Installation, to prevent from re-installing a version you don't want.
After you properly install your new graphic drivers, open up
Display Driver Uninstaller and set this back to default.
And of course, it's always good to backup your registry and make a restore point before doing this.
I also recommend checking the "
Remove C:\AMD and or C:\NVIDIA folders" option, so Windows can't automatically re-install old drivers. The aforementioned option should take care of that, but if nothing else, this might free up some disk space.