|You have a GX260? What is the Service Tag Number of your Dell; it's on a sticker somewhere on the case and can also be found in the first BIOS screen.|
Although the 5200 is a step in the right direction, you can do better. An AGP card is the way to go and there's nothing wrong with a used card bought locally.
Verify you are running Vista Home Premium and have 1.5Gb memory. Look at the psu's in you old machines and check the brand, model, wattage and amps on the +12v rail of those. You might find something to help your situation.
Finally, where do you live and where did you find the $35 video card?