So I recently purchased two new nvidia cards to sli. Up until this point I have been sporting my xfire6950's. I know this is beating a dead horse but I'd rather not let something as simple as a driver issue hamper my gaming come tomorrow. I asked a friend he said I should:
1st: Remove the old cards
2nd: Install new nvidia cards.
3rd: Uninstall AMD drivers.
5th: Install nvidia drivers.
Your friend got the sequence out of place in a couple spots. This should do it.
1st: Uninstall AMD drivers > Shut down PC
2nd: Remove the old cards
3rd: Install new nvidia cards.
5th: Install nvidia drivers
Be sure to only use the latest drivers downloaded off the Nvidia website.
Use the "Custom Install" option and only install those driver components you need or want; at a minimum the graphics and PhysX drivers. i.e. Don't install the 3D Vision driver if you don't use 3D Vision, etc. You might want to try out Geforce Experience though, which is part of the driver package. It is optional.
Select the checkbox to perform a "Clean Install", which may not be necessary on a first time installation, but can't hurt.
After that, once everything's up and running, be sure to go into the Nvidia Control Panel and configure things the way you like them. Always set PhysX to Auto.