GX-280 I have a older DELL computer....?

You have a 32bit system. It reads or uses not much over 3GB of memory. Depending on which model of the 280 you have, there are 5, yours may include a PCIe X16 slot for a graphics card. But this is X16 only, not X16 2.0 which most cards are today. Your choices are limited here, especially with a single core processor. The computer dates back 6-8 years. Suggestion: It is time to upgrade to a newer more efficient computer. Currently the computer you have is good for Email , surfing the net, and basic computer needs, and that's where it ends. I retired a older Dell a year ago from daily duty for the same reasons. Uses now for it are just pinball and card games. Hope it helps.