First of all, get the concept of consoles out of your head. PC's run games better, and are easily upgradable. You cannot upgrade a console.

As far as the Dell...ahem. Look into getting a new vid card. 16MB vid card isn't gonna cut it for many new games coming out. The 256MB of RAM is plenty, so start looking at your vid card. I would suggest the GeForce series (they work with everything). Try out the GeForce3 Ti200. It's cheap and runs great.