Mp4 player won't accept files
 

My daughter deleted all the files on her mp4 player .It is a no name 4 gb player. Now when I plug it into the usb port on the computer it pops up as a removeable device F drive. It has no files on it and won't let me put any in it. The player has no video or music files on it but the fm radio , record and games still work.I have tried to format the hard to no avail. Checkdisk is the same. The firmware isAct2097_272_1 2006/10/30 9.0.60 2006/10/30. Does anyone have any ideas. Thanks