I've always been wondering about this, so I figured I'd post my question here and see what I get.

When updating drivers (let's say for example nVidia's display drivers or nForce drivers) you usually download a setup program for the new drivers first. Is it safe just to run the setup program for that new driver and have it overwrite the old drivers, or should I remove my old drivers first?

When uninstalling old drivers, if you a prompted to reboot after the uninstaller completes, do you have to reboot right there, or can you go directly to the setup program for the new drivers, and then reboot?

The reason why I ask this is because I have some drivers that I nLited directly onto my windows install. If I uninstall the drivers and reboot, the drivers are reinstalled automatically when windows comes back up. Are the drivers truly uninstalled before rebooting, or do I have to reboot after running an uninstall?

What happens if I uninstall a driver, select No for the reboot option, then run the installer for the new driver?

The best practice (which I never use) is the following:

1. Uninstall any software package from Add/Remove Programs (or Programs and Features) for the specified device.

2. Restart into Safe Mode and remove all instances of the driver from Device Manager.

3. Restart into Normal Mode.

4. Cancel the Add New Hardware Wizard (if new drivers have no installer)

5. Install the new driver package installer

6. Restart

what do you do if windows reinstalls the old drivers as soon as you reboot, with no option to cancel?

You can rename the windows\INF folder to OLDINF, or find the driver INF in the folder and delete it.

Though once you have removed any software that may have been installed for the hardware you should be able to just run the driver installer and have it update the driver and install the new software.