If you have a desktop machine (laptops wouldn't be upgradeable), you can find a video card that should run the game for $20-35 at the bottom end. Which kind depends a lot on what sort of slots your machine has available, if any (the current PCI-Express is cheapest, while the older PCI and AGP types cost more and are less powerful). Unfortunately without knowing what slots you've got, it's hard to be more specific about what you'd need to get and what it would cost you.