Which motherboard do you have..?? The card requires a pci-e 16X lane.. When connected to the second pci-e lane on some motherboards, it operates at 1X (may be more with nowadays mobo) and thus the card does not gets detected.. The second pci-e lane is only used by the secondary video card with full effect when the primary lane is filled.. But i guess this problem does not comes with a X58 board as it has two active pci-e 16X lanes..