With the P4 being your potential bottleneck (considering you're running an 8800 series VC and 2gb of RAM), reducing your resolution by a notch definitely should improve your frames and smooth things out a bit. Secondly, I also see you're using the onboard sound. IMO, onboard sound for gaming is still a no-go and you will free up some CPU cycles by adding even a mid-range sound card. An X-Fi option like this one (
http://www.bestbuy.com/site/olspage....=1156203598151 ) is cheap and will improve your sound possibilities considerably.
So, 1.) Drop your resolution to 1440x900 and 2.)add a sound card and you should be fine.
Hope it helps.