Bradders,
The hack can be difficult to remove and will sometimes survive a fat32 format. The only way to be 100% sure is to pop the back off the player and check the chip serial number. The sizes and serials of Hynix and Samsung chips are posted
HERE
A double format with the MP3 Player Disk Tool will generally clean it up as well. You need to go to the Partition Encrypt tab and move the slider all the way right and apply to format, then move it back all the way left and format again.