Why is my xbox 360 disc broke?

I have guitar hero 3 and it is broke for some reason. I had it IN my xbox and moved my xbox from my basement to my room. And when i try to play the disc my xbox says it is an unreadable disc, or a white screen comes up and says something about xbox 360 not being able to support the disc. Any reasons why it's broke? Are there any ways to fix it?