I have a Dell PowerEdge 2850 with a brand new install of Windows Server 2003 R2 x86 edition. All devices are installed and the server seems to be working perfectly. However, when I pop in an AJA video capture card, PCIe 4x-lane, the device manager doesn't see it. There is not even an Unknown Device. 

Based on figure A-5 from this tech spec, I know I have plugged in the card into the correct 4x slot on the PCI riser. I even tried plugging the card into the 8x slot, which also did not work.

What am I missing? Is there something I need to enable somewhere to get the server to recognize anything plugged into the PCI riser card?