Be sure the bios is configured correctly. If it is, then get rid of it completely I.e. uninstall it, plus driver, uninstall any associated software, run cc cleaner or similar to cleanse the registry, remove all folders including hidden folders (there will be one) in program data & try again.
If it still won't go in, try it in compatibility mode. Nvidia installs can be fiddly & they do leave tendrils around the system. Sometimes they're just dogs - I had an Nvidia 7300gs which was just a pig under any configuration, but I've not heard negative stuff about your card.