I'm trying to copy more songs on this MP3 player, but I'm getting the message: "The root of drive E is formatted with the FAT file sytem and can only store a limited number of items. Store the items in a subfolder, or reformat the drive using the NTFS file system." How do I do this, or how do I create a subfolder? When I try anything, I get a message that the content of E will be erased. How do I do a backup of drive E. Thank you so much.