That video card needs an AGP card slot. If your motherboard doesn't have one (and most gateway/dell/poc boards don't) then you will not be able to use that card.
If you are wanting a minor upgrade to your graphics your only likely option is to get a PCI graphics (NOT PCIe, but PCI card). They are not very powerful, but likely better than your current onboard graphics (assuming that is what you have).
Good luck!