Help! Installed Bootcamp on iMac and now I can no longer access my Mac OS!

Question

Hi ALL,
I'm hoping someone can help... I installed Windows 8 64bit on my 27" iMac and downloaded all recommended drivers. However, now I can only load the Windows partition.
I've tried restarting my computer and have pressed 'option' when restarts and the only harddrive option available is EFI Boot and if I click that it just loads Windows 8.
I've never used Bootcamp before and I'm slightly concerned I have somehow wiped my Mac OS off my computer. As I type I am on Windows Internet Explorer - it's a dark time!
What I'm asking is how do I get my mac hard drive to appear / my mac OS to load back up and not windows?

Answer 1

You will need to reinstall OS X:
Reinstall Lion, Mountain Lion, or Mavericks without erasing 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
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 then click on the Repair Permissions button. When the process is completed, then quit DU and return to the main menu.
Reinstall Lion, Mountain Lion, or Mavericks
OS X Mavericks- Reinstall OS X
OS X Mountain Lion- Reinstall OS X
OS X Lion- Reinstall Mac OS X
     Note: You will need an active Internet connection. I suggest using Ethernet
                 if possible because it is three times faster than wireless.