Problem with resolution

Hi.

I recently installed Windows 7 on my laptop.
I went on Crossfire and realized there was two black borders on both the right and left side of the screen. It was like if my screen was 800x600 when I am in game.

I had vista not so long ago and I didn't have this problem. The game was fitting my screen perfectly, but since I installed Windows 7, it does that.

I was wondering if any of you guys/girls had this problem before or has any suggestion on trying to fix it.

Thanks in advance.