check that you have both the 24 pin and the 4/8 pin power connector connected to the mb. the video card need the right amount of power from the pci bus to work. have you tried moving the card to another pci video slot to see if it the slot or the card. have you checked that the pci video is the first video device in the bios. if it is all i can add it it could be a bad card or the power supply not outputting the correct voltage to power up the video card when loaded.