Weird Issue when playing games on external monitor

Hey guys. I'm pretty new to Macs so feel free to laugh at me if there is a simple solution to my problem that I just overlooked. Anyway the thing is when I use boot camp via my external monitor games run at like half the speed as they do when i run them off of just the laptop screen. HL2 runs at like 15 FPS when its hooked into my external monitor. This only occurs in bootcamp ( I run WOW in Leopard and it runs perfect either via external display or laptop screen). What could I possibly be doing wrong? I'm on a MBP 2.2 8600XT and I have the latest video drivers.

 

The res on the monitor is only 1280×1024 its an old monitor so I don't think its that. Its not even slightly slower on the external monitor I mean its like a night and day difference performance wise. Smooth as silk to choppy as all hell.