Have you tried a different video card in that board? If not, give it a try and let us know how it goes. If it's still not working, reset the CMOS (plenty of people have topics on how-to. If the board is UEFI, there should be an answer for that too) and try it again. It could be a bad slot but more likely, it's just an incompatibility issue. Such as, the video card being a newer PCI-X version or being to old (old is a seldom occurring though, most all boards are reverse compatible) Or, the power connector from your PSU to the card could be faulty (That's an often missed reason). Let us know how these checks go for you.