In control panel, the display Icon and then the settings tab and then the adv button at the bottom
-the adapter tab
-look at the adapter type, should be your card listed there
-check out what you have listed there in the properties box
Where you see the Red X, right click on that and choose uninstall and say OK and let it restart and when restarting go into BIOS and check below info
In the BIOS, did you turn off all PCI or just change the primary graphics to PCI-e x 16?
Once back in, check device mgr again to see if it returns and see if below helps out
If does come back with X, right click and choose properties and the driver tab and choose update and let it search the web for updated drivers to see if it can find anything
check out this page and click on Option 2 and see if anything comes of it
Drivers - Download NVIDIA Drivers