Problems with Mac OS X Leopard Install DVD

Sounds like you've got a bad CD. Obviously check for scratches that might have occurred in transit when they shipped it to you. Other than trying to use some of the scratch removing gel, your best bet is to call Apple and ask for another CD.

"Try a new DVD, but that looks pretty serious - it's usually a hardware fault, I assume it's the DVD drive.

Try cleaning the drive, and try either copying a disk to test it or using The Apple Extended Hardware test (reboot with system disk in drive and hold down 'd' key)."