My dad has dementia - does not remember his password. His hard drive has been erased. We need to reload Mountain Lion and can't figure out how to do it.

Question

My dad has dementia - does not remember his password. His hard drive has been erased. We need to reload Mountain Lion and can't figure out how to do it. Internet recovery asks for his Apple ID and password. He has no idea. I have an Apple ID but have never bought anything through the iTunes store so it won't accept my Apple ID. I don't know if his computer is under warranty. He does not remember if he has Applecare. I tried reinstalling Leopard -- the computer originally came with Leopard -- but the computer screen goes grey and a message comes up saying I need to restart. He wants to give this computer to me since it's useless to him. What do I do to get a system on it again?

Answer 1

You will need to reformat the hard drive to go back to Snow Leopard or Leopard.
Does he have a Snow Leopard Disk? He should, as there is no way to go from Leopard to Mountain Lion without it. If you can find the Snow Leopard Disk, I'd at least start with that.
You will need to use Disk Utility in the installer to format the hard drive and get rid of the recovery partition.
Boot from the installer disk by holding down the C key on restart. When it boots, Open Disk Utility (Utilities menu, at least in Snow Leopard).
Select the Hard drive and then click the Partition tab.
Select 1 Partition from the partition menu.
Select Mac OS Extended (Journaled) as the format.
Name the drive (Macintosh HD is the standard).
Click Apply to partition the drive.
When it is done, quit Disk Utility and install the OS.