I got a new alienware area 51 and I got the top of the line products installed such as x2 Ha Radeon 5870's crossfired
intel core i7 quad core processor (2.8ghz)
12GB of DDR tri ram

Now my problem is that whenever i play games it runs them smoothly but when i bring up a web browser in the background it starts to lag my game but FPS doesnt drop, my screen just lags.
also i hooked up a second monitor and when im playing say WoW or crysis on one monitor its fine but once i bring up the web bowser on the other monitor it starts lagging. please help if you know what i have to do.