Make sure a monitor is plugged into it. Windows won't see the card without a monitor.
Really? So if I have 5x 5970s plugged into a windows machine, I would need 5 monitors to see it?
GPU Caps viewer (and thus windows) can indeed see/access the GPUs.
For some reason they are listed as devices 8 and 9, while my 5870 GPU is listed as device 1.
Any ideas?