Is the VIA Unichrome S3G IGP card a factor in determining if my PC can support PCIe graphics cards? My computer said PCI slot 0...but I don't know... I'm about to buy a new graphics card, thats why.

Your motherboard is the main factor in determining whether you can support a PCIe video card. PCI slots are not the same thing as PCIe slots. Indirectly, since IGP works with or substitutes for AGP, my guess is that you don't have a PCIe slot on that machine.