Correct procedure for updating NVIDIA drivers?

Uninstall old drivers, restart PC, run driversweeper, restart PC, install new drivers.

You can just run the installer; this keeps the old files/installer around if you need to downgrade in the future. That being said, this leaves the possibility of .dll conflict, especially if a new .dll is created/removed between releases.

Windows basic display drivers.

Uninstalling first is really quite simple, and a lot more certain.

new driver ready to install / control panel / add/remove programs / select driver / select remove display driver only / do it / restart / install new driver / restart / enjoy.

I've never had to use a cleaner, or had much troubles with drivers doing it this way.

As I said, you don't HAVE to uninstall, its just highly recommended. As long as you don't skip WHQL releases, you should be able to simply install over the existing drivers, although any signs of trouble should lead to a driver sweep. All old drivers are stored on the computer by default, although as the .dll files are never referenced, should not cause any conflicts.

All GFX cards can display 640x480, 256 color native, as required by M$ standards. If no display driver is present, this becomes the native resolution.