sorry, editing again (i thought u had SiS)
anyway, as you have VIA, the Only VIA chpset for LGA775 that came with onBoard graphics was P4M800 Pro chipset, coming with UniChrome graphics, and also it does comes with external VGA support but for AGP only (not the PCI)
so you have to get a VGA card with AGP slot, which you can buy both in nVidia and ATi as well, for surety, open your casing and you'll see a Brown color slot just below the CPU (the first slot). that is AGP and can support your graphics card with AGP format.
Intel Core2Quad 2.66Ghz 12MB L2-Cache
4096MB DDR Kingston Hyper-X
XFX 9600GT AlphaDog
Seagate 2 X 320GB SATA2
LG L246WH Flatron 24"