Just to chime in, did you try Judas' suggestion about the Crossfire cable? As mentioned AMD has allowed a "soft" interlink through the PCIE bus, so the Crossfire cable wasn't always necessary (I do recall some drawbacks though, but I can't recall to what degree... speed I think). To that end what I would suggest as a trial: - shutdown the computer, and pull the Crossfire cable. If you don't have both cards installed, do so, but don't hook up the Crossfire cable. - reboot the machine, go into the bios, and (if I recall) under "Peripherals" set "Initial Display Output" so that it says "PCIe 1". Save, and reboot. If it works Windows should see both cards. If it does this would indicate an issue with the Crossfire cable. If it doesn't however, at this point I'd be looking at the power supply.