My current computer has an NVIDIA Geforce video card. It will support two monitors, for editing, and has two monitor out-ports. Only one (1) of these video card monitor ports will work....'could be I need a different driver, a second monitor, or something... While the video card is in place, the motherboard's monitor port also will NOT operate. You might want to try removing the Video Card, and then see if you have output from the motherboard's monitor port...
Good Luck! rcgambler.