try this forums.xbox.com/.../624.aspx if those tips do not work then sadly you will have to send in your console for repair, good luck.
XBOX 360, kicking other consoles backsides since 2005.
This problem has to do with the laser in the disc drive. There is no way to fix it without taking the xbox apart, so you will have to send it in for repair. I would do this asap if you stiff have the warranty or it will cost $100 for the repair. Sorry