Isso é o que recebi de uma rápida pesquisa do Google .
Inicializando a partir de sua unidade de CD / DVD ou disco rígido externo
Every new mac comes with a Boot CD or Boot DVD for re-installing the operating system (OS) at some time at which the initial install of the OS has reached its sell-by date. This CD is the easiest way to get the machine booted and in a state where you can run some basic tests and fixes using the Apple Disk Utility available as part of the install process.
I am going to make the assumption that you are unable to boot the Mac to a state where you can reach system preferences, so I will disregard the “Startup Disk” selector in a System Preferences as a means by which to select the CD as a boot disk! As an alternative, startup the Mac, as it whirs into action, slot the CD into the drive and then hold down the C key. This will force the Apple Mac to attempt to find a valid system folder on whatever media is contained int he CD/DVD drive and use it to boot the Mac.