There are two possibilities: you have run into the PCI-E 2.1 compatibility problem that some PCI-E 1.0 boards have, or you got a bad card. If possible, try running the 6870 in another PC. If the 6870 works on another computer, it's the PCI-E 2.1 compatibility problem. Check your motherboard manufacturer's website for a BIOS update for your board. Some of the boards with this problem will only run 2.1 cards with an updated BIOS. If it is the compatibility problem and there is no BIOS update that addresses this for your board, you'll need to either get a new motherboard that does support the 2.1 cards, or RMA the 6870 and look for a PCI-E 2.0 card. None of AMD's current cards use 2.0, they are all 2.1, so you might have to look at nvidia for a 2.0 card if you need one, or look for an HD 5000 series card that is PCI-E 2.0.