You can download a free program called Driver Sweeper that will seek out and delete Nvidia left-overs. Uninstall the drivers through Control Panel/Uninstall Program, reboot, run Driver Sweeper, select Nvidia Display drivers, anolyze and Clean, reboot again, and install the new drivers. Windows New Hardware Wizard may get in the way when you reboot, but as long as it just installs a standard VGA driver, you can proceed with the Nvidia install.
You missed a step. After manually uninstalling,
reboot into Safe mode, then run Driver Sweeper.
But yeah, Driver Sweeper does a good job.