I recently found my old MiniDisc Play which is a sony MZ-R500 and a whole bunch of minidiscs. I started to use it to record live music a local places and such. My question is how do you erase old MD-LP disks? I have bunch of used ones with music I have already transferred on to my computer. Every time I try to record over the disk i get a flashing message that says SORRY and nothing else. I would be great if some one could help me with this issue