Hi Paul! It's a reasonable question. Actually what won't delete is a folder that contains an old backup of data from the unit. Quite recently did a hard reset of the unit, after also reformatting the flash drive, that that old backup folder just seems quite determined to stick around. Haven't really tried to delete other things because after all, other stuff that's on there I need to hang onto, but you know, anything might be worth a try as long as I haven't done it already. *lol* Cheers, Dave