HP 8430F Desktp wiped clean..need video to work

I have a HP 8430F desktop that I bought used from a electronic store through Ebay. It was wiped clean before being sent to me. I have the original HP recovery disc's to install Vista 64bit back on the PC. I am trying to get some video output to see what the PC is doing, but I am unable to do so. The PC was sold as being full functional, so I think it is something I am doing (or not doing) that is not allowing video output. The PC comes from HP with a video card already installed in the AGP slot that only has these outputs (HMDI, DVI, and S-Video). The built in video in the motherboard has a black cap screwed over the output on the back of the PC and says "Do Not Remove". I am unable to get any video source output from the PC. I am thinking it needs drivers to allow the AGP card to work? Any help would be greatly appreciated. Brad2157@yahoo.com