Choppy game play after switching from Win7 Ultimate RC to Pro

[unclejunebug]

Hey all,

I was previously running the 32-bit Windows 7 Release Candidate until just yesterday when I installed a copy of Windows 7 Pro 32-bit. With the RC I could play games like L4D2, TF2, and L4D at very smooth frame rates. After installing Pro my game performance has hit the crapper. I've been running FRAPS to check fps and it ranges between 10 - 60 during game play but regardless of the fps it shows the video is very choppy. What seems weird is that the recommended video settings that Steam gives is to run all video options at High so I tried lowering them all to Low and it got worse. Any ideas? I'm stumped.

I downloaded the most recent Nvidia driver from the site and the rest of my system specs are in my signature. Thanks in advance!