The easiest thing to try first: Go to Display Properties>Settings tab>Advanced button>Adapter tab>Change button. Point the wizard at the location of the drivers you want to use.
Alternate methods:
Boot into Safe Mode, go to Device Manager and remove the Nvidia video adapter. Reboot back into Safe Mode and try reinstalling the drivers you want to use. Sometimes that works, sometimes it tells you that it can't install in Safe Mode.
If it won't install in Safe Mode, reboot into normal mode and if you're quick you can stop the automatic installation of the new drivers. If so, you can use the Add Hardware wizard to point it at the drivers you prefer.
Now you know why so many people don't get driver updates from the Windows update site. The drivers there are kind of generic...sort of a "one size fits all" approach. If they fit, great, but they often don't as you have discovered.
