The video card looks
MORE than fine for running MAME (not much video card needed) or Visual Pinball/Future Pinball. (lots more video card needed)
512 MB of ram
Looks like this might be a big part of the problem. Bump it up to at least 1 GB, preferably 2 (maybe even 4) and I think you'll like the results. Should cost you around ~$20-80 (not sure what variety of RAM your motherboard needs) and do
way more for MAME than the card did.
If your MB can handle it and you can find a deal on a used 6000+ (Amazon has one for $75 used at the moment) you can triple your processor power, but considering the expense of buying the new video card, RAM, and processor, you might just want to return the card and take the plunge to get a new system.
If you don't take the plunge, consider fine tuning what processes are running. After 4 years, who knows what you've got running in the background.

Scott