Have you disabled the IGP in bios and uninstalled the ATI drivers before installing the nVidia drivers? There is no reason they wouldn't be compatable that I know of.
Yeah, I read somewhere that you needed to disable the Onboard graphics, and my bios had something called Internal Graphics Mode, and the manual didn't explain what it was at all, but it was the only thing I saw that had to do with video. I disabled it, and now I can't even see anything at all when I boot up.
Can you help at all?