The spec req for this game isn't that high. It's optimized pretty well I think.
I'm playing on low settings at 800x600 and get 30~50 fps.
Game still looks good on low, well for me anyway, I play every game on low.
I have a 4 yr old computer with a $30 graphics card.
Windows XP
AMD Athlon 64 X2 Dual Core Processor 4200+ ~2.2GHz
2 gb ram
8600gt 256mb ram
You don't need a super powerful graphics card if you don't mind running it in low, just get a cheap one and it should run fine.