Before such an extreme solution try this instead:
Reinstalling Lion/Mountain Lion Without Erasing the Drive
Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.
When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the main menu.
Reinstall Lion/Mountain Lion: Select Reinstall Lion/Mountain Lion and click on the Continue button.
Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.
I definitely do not have a Snow Leopard DVD. I have one that says for reinstalling Leopard. I am wondering if when I bought the computer from Best Buy and I let them set it up if they possibly installed Snow Leoprd on it. I know that is what I had on it as I only upgraded to Lion and then Mountain Lion. Anyway I finally figured out the instructions that were sent and I went into the disk utility menu. It shows that my HD is good and then I attempted to reinstall OSX Mountain Lion. After a 2 1/2 hour download it started install OSX. After about 20 minutes it showed a failed message and sent me back to attempt another install. This time it never showed my Mac HD as an install option. I went back again and verified the HD in disk utility. All showed to be good and I attempted another install. This failed immediately and showed I did not have enough space on the HD. I again went back to disk utility and again attempted to install OSX. This time when I tried to select the Mac HD it showed it to be locked. Is my next course of action an erase and reinstall of the software? I don't even care about Mountain Lion, I just want the computer to start up again.
Then you need to purchase a copy of Snow Leopard. You cannot install Leopard, Lion, or Mountain Lion without first erasing the hard drive if you don't have Snow Leopard installed. You cannot reinstall Snow Leopard without a Snow Leopard DVD.
Upgrading to Mountain Lion
You can upgrade to Mountain Lion from Lion or directly from Snow Leopard. Mountain Lion can be downloaded from the Mac App Store for $19.99. To access the App Store you must have Snow Leopard 10.6.6 or later installed.
If you need to purchase Snow Leopard you can still purchase a copy from Apple's online store's telesales agents.[1-800-MY-APPLE (1-800-692-7753) or Customer Service and Sales Support at 1-800-676-2775.] Ask for a Sales Representative.
Third-party sources for Snow Leopard are:
After you install Snow Leopard you will have to download and install the Mac OS X 10.6.8 Update Combo v1.1 to update Snow Leopard to 10.6.8 and give you access to the App Store.
If you need to purchase Lion call 1-800-692-7753 or 1-800-676-2775. Ask for a Sales Representative. They will check your Apple ID, and email you a code and instructions. The cost is $29.99 (as it was before) plus tax. It's a download.
Be sure your computer meets the minimum requirements:
Macs that can be upgraded to OS X Mountain Lion
- iMac (Mid 2007 or newer)
- MacBook (Late 2008 Aluminum, or Early 2009 or newer)
- MacBook Pro (Mid/Late 2007 or newer)
- MacBook Air (Late 2008 or newer)
- Mac mini (Early 2009 or newer)
- Mac Pro (Early 2008 or newer)
- Xserve (Early 2009)
Are my applications compatible?
Am I eligible for the free upgrade?
For a complete How-To introduction from Apple see Apple - Upgrade your Mac to OS X Mountain Lion.
No problem, I tired a reinstall of OSX Mountain Lion yesterday morning with Apple Tech Support on the phone with with the whole time. It loaded fine and things are working again. They are sending me free of charge a Snow Leopard back up disk. They said I should have had one of those instead of a leopard disk.