That's why people have created Disc Images on harddrives of these games and then burn CD-Rs and use modchips to play them. If your disc gets scratched up and won't play, throw it away and burn another one. One of the legitimate uses of "backups". Ofcourse the other is that you never have to worry about finding a playable copy of some game anymore, you just obtain and image and burn it to a cheap recordable disc.
