I found a really cheap Xbox at the local thrift. It turns on, but takes quite a long time to load discs and can't even get past main menu screens. It goes back to the system menu with a DRE message when attempting to load anything in-game. Is this a common problem that can be fixed by a quick cleaning, or is there more to it? I'd rather not even bother opening-up the system if the fix isn't going to be simple or cheap.