My friend has a problem with his Xbox, its not modded or anything. The most common problem is the Xbox will randomly just turn off, and then he has to turn it back on. Also, but less likely to happen is the xbox will freeze, everything on the screen will stop, and he has to turn it off, and turn it back on. A really rare problem, that often happens after he just starts hitting buttons randomly and turning it on and off (because you seriously cant play the thing for more than 5 minutes, its really annoying) he gets the Your Xbox Needs Service thing in a bunch of languages and a number 21 at the top. We also noticed that if you jiggle the AV cord the screen flickers ALOT where mine doesnt do that at all. He bought his used, but the sticker on the bottom doesnt seem to be broken or anything so i dont think its someones failed modchip attempt. He is willing to open the Xbox to fix the problem at this point so any help would be greatly appreciated.