Solving an inability to boot from Mac OS X CD/DVDs
Posted in digital video news
Try holding down the “option” key instead of the “C” key For some reason, holding down the “C” key at startup does not always work to force booting from media that is in your Mac’s optical drive.
In these cases, holding down the “option” key at startup (which, when functioning normally, displays all available startup devices) may allow you to select the appropriate boot volume (your Mac OS X installation CD or DVD) and proceed with the normal booting process.Failing this, try holding down the “Command”, “Option”, “Shift”, and “Delete” keys simultaneously while your Mac is starting up. This should force the system to bypass the normal startup volume and look for another valid boot drive — namely your Mac OS X startup CD or DVD.
Read the whole article on MacFixit: click here