My hallmate's powerbook recently started going on the fritz. I'm unsure what exactly the symptoms were, but he took it to the apple store and they said that it may be the hd. So he's tried to install the same hd twice, which was reformatted and erased using disk utility through my mb pro. Problem is when he boots up holding the "c" key and the boot cd, and goes to install mac os x, the hard drive doesn't appear. What could be the cause of the hard drive not appearing durin os x installation??