That's not a bad machine that you have gotten yourself there.
My only concern is the video card, which isn't too hot. If you wanted to upgrade it to something faster, you would need to upgrade your powersupply, and upgrading a dell power supply is difficult.
I would suspect it will run every game, but it won't run the newer games (Oblivion, BF2, etc) very well, possibly it could at the lowest settings.
It would be well worth it to spend $100-$150 and get a decent mid level videocard (7600gt or better), but if you aren't an avid gamer, what you have should last you awhile. Your processor, btw, is a very good one.