I replaced the hard drive on a mac mini and needed to reinstall OS X. Unfortunately, my copy of the Leopard DVD would not boot the mini, or my MacBook Pro -- the computers both just spun it up and down multiple times before ejecting it and displaying the circle-with-a-slash symbol. On closer inspection, the DVD was scratched, but would still appear fine within finder. This is my work-around to install using an iPod.
Step 1: Make an image of the DVD
Make an image (.dmg file) of the DVD. I did this through Disk Utility.