I had the same problem with my MP4 player. I turned it off while it was playing, when I turned it back on it started to give me the same "disk error" all the time. Searching here and there I came up with this solution, I hope it works for you also! Connect the player to the computer. Next, click on start, then click on 'run'. In the box, type 'cmd', then click OK. Now type cd\ and then hit 'enter'. Now type format/fs:fat and the letter assigned to your MP4 and then hit enter. (Example: format/fs:fat e:) It will ask you if you want to format, so say yes. In the middle of the process, it will ask you something about clusters, so say yes again. In the end, your MP4 should work. However, all your files will be deleted, so you will have to put them all back. Like I said, it did work for me, I hope it does for you also.