It's likely that your portable MP3 player might be infected by viruses or something undesirable leading you to woes. And you might have formatted the MP3/MP4 player to remove those common hassels.
Hey, wait did you notice your MP3 player display file system error on its 3" TFT? You're a single minor mistake might have caused this. File System Error is displayed when incorrect file format is chosen while formatting the disk. If the disk is larger than 2GB, it's better to format in FAT32 File System and NTFS, is your choice.
Since most of the MP3 players or pen drives are around or less than 2GB, so format them using FAT file system. And you better convert your music from WMP if you like!