Black border on my desktop?

I was playing maple story one day, and then it reverted to my desktop and said something about a VPU recovery. I don't really know much about computers, I know enough to keep me up to date like installing stuff, updating drivers, and etc. But I have no idea how to fix this problem. Now I have a black border around my screen, that I can't move my mouse on, thus making every single page smaller.
Can someone help me with this?