I have a 4gig flash drive but i think i can get a hdd to work on it needs to be formatted in fat32 and the music files need to be in folders. gonna try it i'll let you know if i get it to work.
I plugged in a laptop hdd with a usb to IDE adapter and it worked like a charm. So pioneer does support Hard Drives. Just format them with fat 32 and load it up with music.