What is the best way of making a backup copy of my leopard 10.5 upgrade dvd ? Should I use a different program or disk utility to make a image of the dvd ? I made a .cdr backup with disk utility clicking new image , is that good enough ? Will it be bootable when I burn it to a dual layer dvd ? I want to make a backup in case I ever loose my original copy or if it gets scratched , also leopard install dvds are really expensive now so I don't want to ever have to replace it that's why I need a good backup for it .