well alot of overheating problems have been because of the power supply being faulty, also can get a bit warm if on carpet etc, so if possible try a mates or somthing. If it is your xbox and if got the 3 rings that if it not under warranty and you dont want to pay to have it repaired that are various diy method that google can lead you too but they might make the sitaution worse
They have got a knobbers rep for scratching disks when moved with them in.
If you haven't already try this
http://support.microsoft.com/kb/909819
Also i tend to do this whenever somthing goes a bit dodgy, doesnt erase anything that is needed or important
:
Go to the system blade and then select memory.
Press Y on the HD symbol and then press X,X,Left Bumper, Right Bumper, X,X. Once you do this a messsage will appear saying: Do you want to perform maintenance on your Xbox 360 storage devices?