FRAPS (Screen Recorder) leaves black bars on the sides?

I've been recording with FRAPS for a while (this is for youtube). I record gaming and such. When I record games like Minecraft it records perfectly, full screen no black bars. But when I record steam games, it leaves black bars on the sides, with each game. They all go Full Screen which I think has something to do with it. I have games like Fallout 1, Left 4 Dead 1 and 2, Portal 2, Team Fortress 2, and I just recently got Modern Warfare 2. I tried recording MW2 but the video was square so it left black bars. In full screen the game takes up the entire screen so I would think it should record it that way. But it shrinks it into a square. My FRAPS movie settings are 30 FPS, Half Screen,Loop Buffer Length 30 seconds. Any help would be greatly appretiated! :)