what to do if your disk tray does go in the back out?
 The first is to replace the tray drive belt, easily found via eBay etc. These stretch with use, stiffen with age or may get greasy, whatever the reason it causes the belt to slip resulting in the fault.Lightly slam the top of the Xbox where the disk drive is as it tries to open. There's IIRC 3 or so times it tries to open. Hit the top of the Xbox when you hear a slight knock. You'll have to leave a disc in the Xbox at all times in order for it to open now. 