Thanks for the suggestions, but I was able to resolve the problem. The integrated VGA adapter needed to be disabled in the BIOS before the card would produce output, and as the adapter Windows 2008 R2 used. Just FYI. The reason for the new graphics card was not for display on the server. I use the Dell R710 to stream home movies, and Apple iTunes 12.1 + versions do not support the internal card any longer, so new movies cannot be added to the iTunes library. Now that Windows 2008 R2 is using the new card I can once again add movies  to iTunes and stream them on my networked Apple TV's.
I have a PowerEdge R710 with Windows 2008 R2 and installed a NVIDIA GeForce GT 720. The Windows drivers appear to have installed correctly, and all looks good in the device manager, but I have 2 problems. Is there a jumper on the motherboard that disables the built in adapter and enables the PCI Ex8 card, or a BIOS setting? Or is it just incompatible? Although that would be odd as Windows recognizes the card and installs the drivers without a problem. Any help would be greatly appreciated!
Dell PowerEdge R710 and NVIDIA GeForce GT 720