I built my PC about two years ago. I have 2 MSI Radeon HD 6850 video cards installed with crossfire. They were both working until last week when I tried to hook up a third monitor on the second card. But Windows only recognizes one video card. I have tested the second card in the first cards slot, it works. I've tried uninstalling and reinstalling the drivers, swapping the cards, I've even done a fresh install of Windows. All of my drivers are up to date. I have no clue why it just stopped working. Not sure if the PCI-e slot just went bad on the mobo or if it's a software issue. I ordered a PCI-e riser ribbon cable. I have one extra PCI-e slot on the bottom of my mobo, but the psu is blocking it due to the fan on the video card.
Motherboard: Gigabyte ga-990xa-ud3
Video Cards: MSI R6850 Cyclone PE Radeon HD 6850 Video Card - 1GB, GDDR5, PCI-Express 2.1 x16
Power Supply: Cooler Master Silent Pro M - 1000W
Operating System: Windows 7 64bit Home Premium
Motherboard: Gigabyte ga-990xa-ud3
Video Cards: MSI R6850 Cyclone PE Radeon HD 6850 Video Card - 1GB, GDDR5, PCI-Express 2.1 x16
Power Supply: Cooler Master Silent Pro M - 1000W
Operating System: Windows 7 64bit Home Premium