Don't know the required system, and I can't find any suggestions of it, but 256MB of RAM isn't barely enough to boot XP, let alone run a decent game
Considering the prices for memory these days, you should be able to boost to at least 512 without breathing hard... and if your OS will take it, to a gig.
Decent graphics cards are now cheap too. The *good* ones aren't... 'cause they're still up in the really expensive range... but a 256MB card shouldn't be too costly.
Post your specs and I'll give you my own thoughts of what I'd upgrade on your machine. And then you can take 'em for every penny you paid for 'em
