I would recommend you install the new one, but when you restart your computer, go into safe mode and just disable the Nvidia card in device explorer. Reboot normally, and if all is good (i.e. its indicated windows is using the new card and it's software is controlling everything properly), you can manually go in and get rid of the old drivers (though I don't think it will improve performance, so I'd say leave them- tbh I've never been in a position of having two video cards physically installed at once... I doubt it but windows MIGHT try to run the old one in tandem using a universal 'generic monitor' driver, potentially grabbing resources). If you cant get in go back into safe mode and restore the old device and find out a way to change the priority to the new card (Not sure how to do this, sorry :[ ) Someone can correct me but I believe safe-mode loads a universal driver, the one i mentioned before, so you should never be locked out completely. I'm not exactly sure, I just notice every time I load up a windows install the video card is initially controlled by a generic driver shipped with windows before loading the specific drivers, and safe mode means no 3rd party, so seams like it'd make sense that this driver would be the one used.