If you are plugged into any of the ports on the I/O shield (on top) then you are plugged into the wrong port. On this support page you should be plugged into the GPU labeled #8.
On the back panel of this computer (XPS 8900) my monitor is plugged into the HDMI display port #4. This computer has the NVidia GeForce GTX745 graphics card that's installed into one of the PCI expansion slots. My question is, am I really plugged into the NVidia card OR is there another on board video display that I'm using because I'm not plugged into the video card? Thanks,
NVidia GeForce GTX745 display