I'm going to a gtx 570 from an ati card. I'll be doing the usual uninstall, safe mode driver sweeper removal, install nvidia drivers thing. I've also switched fcrom a creative sound card to a xonar dx card on this same win7 64bit install using driver sweeper to uninstall all the creative files. I haven't had any problems with the sound, do you think these 2 hardware changes warrants a reformat or am I safe with just driver sweeper?
I just always used the ATI uninstaller and had no problems at all. If you go one more step and use driver sweeper, I am sure you will have no problems. Then I do a double check to be sure I am running the generic Windows VGA driver right before your last shutdown and physically change the cards.