Screen Resolutions in Games

When I play any game on my computer it runs using only part of the screen and leaves a big black box around the outside of the game screen. I've tried changing the resolution of my screen and it still doesn't run using the entire screen. Is there a way to fix this or am I stuck with a black box around my game screen forever?

Edit: I put this in the wrong forum...I was aiming for General Discussion. If someone can move it to the proper forum that would be great.