I am thinking about getting the new Nvidia Gforce4 graphic card, but my system is fairly old- 500mhz PIII, 320mb SDRAM with Win98. Will this card work or will it require a more modern setup?

It might work, but why put it in a crappy computer?

You need an AGP slot. If your mobo only supports AGP 2x, you will not be able to put that card to it's full potential. But most likely it will work. But if you are looking to increase performance overall, I would sugggest a CPU/mobo upgrade. That G4 will probably run you near $300. So if you just want to increase overall performance, the money will be better spent on a new system.

Like stated previously, make sure you have a 4X AGP slot, but if so, I'd say it would work pretty good. A card that badass would compensate for the somewhat "slow" cpu. I'm assuming you could probably updgrade the cpu too without changing anything else, if you're going to spend that much on the card, why not spend $100 more on a 700-900 mhz cpu(find out what your motherboard supports), and sell the old cpu for $50-$60.