Swifty, it's because the GF7300LE is there.
It describes it's presence as more than just onboard in the VGA section;
"One (disabled due to the installation of a graphics card)"
As MM mentions he can yank that, and pretty much put an HD4670 or GF9500GT in there without any concern, and probably even an HD4770, GF9600series or even HD5750 if he's lucky.
I would recommend the HD5750 with a good X# days return policy without restocking fee to simply swap out for an HD4670 if power supply proves to be an issue.
*Weird I guess you deleted your question as I was replying, post quote is gone too* Strange