Sei in grado di installare nuovamente Mountain Lion seguendo questo tutorial fornito da link
Follow this tutorial in order to clean install OS X Mountain Lion.
NOTE: A clean install of OS X Mountain Lion will delete all data on
your hard drive. Be sure to backup all of your files before
continuing, and make a list of the apps you'd like to re-install once
you have Mountain Lion running.
Step 1: First things first, you'll need to purchase OS X Mountain Lion
from the Mac App Store; it'll cost $19.99. Once the installer is
downloaded (it'll take a while depending on your Internet connection,
4 GB+ download), don't run it.
Step 2: Head over to your Applications folder. There should be a new
app called "Install OS X Mountain Lion." Right-click on it and click
"Show Package Contents." Navigate to Contents>SharedSupport and find a
file called "InstallESD.dmg." Copy it to your desktop.
Step 3: At this point, it's time to decide whether you'd like to
create a bootable installer on an external hard drive/flash drive, or
a DVD. We recommend going the external hard drive/flash drive method
since it'll be significantly quicker, and that's what we'll show you
in this tutorial. You'll need at least an 8 GB flash drive and/or an
empty partition on an external hard drive of the same capacity. Plug
the external hard drive/flash drive into your Mac now.
NOTE: The following step involves deleting all files from your
external hard drive/flash drive. Be sure to backup any important files
before continuing.
Step 4: Launch Disk Utility (located in Applications>Utilities) and
select the drive you'll be using on the left. Click on the "Restore"
tab and in the "Source" field, use the "InstallESD.dmg" that you
copied to the desktop earlier. In the "Destination" field, make sure
that your external hard drive/flash drive is selected. Click "Restore"
and allow the process to take place.
Step 5: Once the process finishes, keep your external hard drive/flash
drive plugged into your Mac. Restart your Mac and once you hear the
startup tone, hold down the "Option" key. Once the menu appears,
navigate to your external hard drive/flash drive using the left and
right arrow keys and select it by pressing the "Return" key.
Step 6: Once the installer loads, navigate to Disk Utility and erase
your hard drive.
Step 7: Head back into the installer and follow the instructions to
install OS X Mountain Lion.
Tuttavia, se si tratta di Mac nuovi di zecca con file che non ti dispiace tenere a mente, probabilmente lo installerei semplicemente nel Mac App Store. L'installazione pulita è più lunga, più coinvolgente e forse nemmeno necessaria. Tuttavia, è utile per coloro che desiderano rimuovere tutti i file dalla loro precedente installazione con un nuovo inizio. Spero che questo aiuti.