Just thought I would let you have some information. My disc drive started making a very loud grinding sound yesterday evening and wouldn't read any discs. I tried several including Halo 3 and Simpsons (both brand new, enjoying Simpsons but the jumping is a bit hit and miss, could be a problem) and ......nothing
I phoned Xbox support and spoke to a helpful woman, who told me to take the HD off and try to run the games, would you believe it worked perfectly?
She then told me to re-attached the drive and she told me to go to the memory blade, once there press Y and then press X,X,LEFT BUMPER,RIGHT BUMPER,X,X.
I'm not to sure what it did but it had the result of fixing the problem.
I know it's good to share so thought I would tell you guys.
Stone me, What a life!