Last time I wanted to install Mac OS X Leopard on an Mac and had the problem of an DVD that was always reported as "defect" - It could boot but not install.
So, I came around an quite easy solution:
Installing Mac OS X Tiger - and then Updating!
Seemd that my DVD is somehow only scratched where the "Complete Reinstall" Files are.
Ah, and by the way:
I had for ages the Problem of Warcraft 3 etc which didn't wanted to run under Mac OS X (both Tiger and Leopard) in the latest Version.
It always crashed as I choose "Option" in Game.
Solution is quite easy:
Go to ~/Library/Preferences and erase the com.blizzard.WarcraftIII.24 and Warcraft III Preferences Files.
Thats it!