Help PLEASE
 

Help PLEASE! I was deleting songs and etc. Then I unhooked MP4 from computer to see if a movie I put on it worked. It didn't so I hooked it back up to my computer to delete it and I CANT do anything the removable disk thing comes up but I cant open it or do anything.....then I took it back off the computer and the MP4 turns on and everything but it has lost all files as far as music and everything. Problem is that I cant put anything back on it because I cant open the removable disk file or anthing please help if you can I am lost here. THANKS