When your card was not recognized in the BIOS, did you happen to notice if its fan was running, so at least partially alive?
Not sure if the following will work, but pretty simple and worth a try.
All video cards out of your PC, as it is now right? Uninstall the Nvidia driver, but have a driver installer program ready to use. (I had so many problems with the several current Nvidia drivers with EVGA 660 SC cards, WHQL versions too. I wouldn't touch a beta driver, but if you know they are Ok... up to you.
After video driver uninstall, reboot once to make sure all is Ok. On that reboot or yet another, go into the BIOS and save your settings in a profile if you have not done so already. Save and exit, boot into Windows, then shutdown, remove power, etc, put in your video card. While case is open, clear the BIOS/CMOS with the jumper, and even pull the battery for 10 minutes. Removing the battery might also clear your saved profiles, so either pass on that, or know in your head or on paper what the settings are. You'll need to restore them of course after the BIOS/CMOS clear. The CMOS clear is the main step you want to do, sorry I don't know your experience level playing with the BIOS. You didn't mention doing this so if you did already, oh well.
My theory is between putting the other card in your board, and the driver failure, lots of confusion with the video source, and you need to start over. The BIOS/CMOS clear is the main part of that.
Replace the jumper to its normal position, double check the card's connections, and fire it up. You might want to keep the side panel off the case to check if the card's fan is running. You should be prompted to go into the BIOS on that boot, don't just load defaults, it may stay on the on-CPU video. You want to check if the card is seen by the BIOS anyway, right? Fix your BIOS settings of course. Good luck!
If the card is not seen in the BIOS or Windows, something might have happened to damage the card. Back to trying it on the girlfriends PC again. If you cleared the BIOS earlier without removing the video driver, I would try that step again, and then clear the BIOS again.