"Repair disk" when installing Mountain Lion

Question

I was just upgrading to Moutain Lion OS X right now when it tells me my disk needs repair. I tried, but it says "Macintosh HD couldn't be verified properly" (might not be exact wording, it's in Norwegian for me). When I click the "repair disk" button nothing happens, it just gives me the same message.
What are my options? I do have a back up (time machine), BUT it's from 2 years ago and thus I'd be losing a lot of files I have on here since after then, and that would really suck..

Answer 1

Then quit the Mountain Lion installer. Do you have a bootable system on your external hard drive? If so, then boot from it as follows:
Boot Using OPTION key:
Restart the computer.
Immediately after the chime press and hold down the "OPTION" key.
Release the key when the boot manager appears.
Select the desired disk icon of the external HDD.
Click on the arrow button below the icon.
Once you have booted from the external drive do the following:
Repair the Hard Drive and Permissions
Open Disk Utility from the Utilities folder. After DU loads select your internal 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.
If DU reports errors it cannot fix, then you will need Disk Warrior and/or Tech Tool Pro to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.
Restart the computer. Locate the Mountain Lion installer in the Applications folder. Now see the following before proceeding if you want to make a bootable USB flash drive installer:
Make Your Own Mountain/Lion Installer
1. After downloading Mountain/Lion you must first save the Install Mac OS X Mountain/Lion application. After Mountain/Lion downloads DO NOT click on the Install button. Go to your Applications folder and make a copy of the Mountain/Lion installer. Move the copy into your Downloads folder. Now you can click on the Install button. You must do this because the installer deletes itself automatically when it finishes installing.
2. Get a USB flash drive that is at least 8 GBs. Prep this flash drive as follows:
Open Disk Utility in your Utilities folder.
After DU loads select your flash drive (this is the entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.
Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, set the partition scheme to GUID then click on the OK button. Click on the Partition button and wait until the process has completed.
Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.
Set the format type to Mac OS Extended (Journaled.) Click on the Options button, check the button for Zero Data and click on OK to return to the Erase window.
Click on the Erase button. The format process can take up to an hour depending upon the flash drive size.
3. Locate the saved Mountain/Lion installer in your Downloads folder. CTRL- or RIGHT-click on the installer and select Show Package Contents from the contextual menu. Double-click on the Contents folder to open it. Double-click on the SharedSupport folder. In this folder you will see a disc image named InstallESD.dmg.
4. Plug in your freshly prepared USB flash drive. You are going to clone the content of the InstallESD.dmg disc image to the flash drive as follows:
Double-click on the InstallESD.dmg file to mount it on your Desktop.
Open Disk Utility.
Select the USB flash drive from the left side list.
Click on the Restore tab in the DU main window.
Select the USB flash drive volume from the left side list and drag it to the Destination entry field.
Drag the mounted disc icon from the Desktop into the Source entry field.
Double-check you got it right, then click on the Restore button.
When the clone is completed you have a fully bootable installer that you can use without having to re-download Mountain/Lion.
Note: The term Mountain/Lion used above means Lion or Mountain Lion.
As an alternative to the above you can try using Lion DiskMaker 2.0 that automates the process.