I have a MZ-R500 thats meen i record music on MD's only with direct connection in real play time recording. Today when i tryed to erase some old disk's i received " TrPROT " message . this is crazy becouse the disk's are recorded be me and i dont know what kind of protection is this . The only thing i found about this is "TrPROT - track protected. you cannot edit a track checked out from a computer." but i dont have any computer link with this MD . sry for my poor english