before you start, download and install driversweeper.
With that done, uninstall the Nvidia softwares and reboot BUT in safe mode (hold F8 during boot up) and then run driversweeper to totally remove the garbage the uninstall left behind.
Shut down and remove the power lead, wait for a few seconds then remove the old card, then.... fit the new one!
Reconnect the power lead and boot up.
Download the latest drivers from AMD, sweep for virus infection, install, reboot, have fun.
BTW, if you`ve installed/removed several drivers in the past on your current Windows install, use driversweeper to clear them out while you`re in safe mode!