I purchased a second hand iMac with Mavericks Developer installed already, seen as I am not a developer and other things don't work, I purchased a copy of Mountain Lion but when tring to run the installer it gives me this message "alert mac os x 10.7 cannot be installed on this computer" I want to keep all user profiles and software intact so I don't want to wipe the hard drive (although many other posts say when you get that message wiping the hard drive still doesn't solve it)

any ideas?

  • 10.7 is Lion, not Mountain Lion. The computer might have been made after 10.8 (Mountain Lion) was released.
    – dwightk
    Mar 24, 2014 at 19:27
  • I'd say backup your files and wipe it. Wiping the hard drive allows you to downgrade. I know because I've down it before (from Mavericks to Lion) Mar 24, 2014 at 21:18
  • Why not just install Mavericks for free?
    – Alexander
    May 25, 2014 at 8:08

3 Answers 3


Verify that your iMac can run the older version of Mac OS X. You can see what versions can be run by searching for your specific model of iMac at EveryMac

Sometimes I have seen that even if a Mac was shipped with an older version of Mac OS it is difficult to downgrade due to firmware upgrades that make the system incompatible with older releases. I haven't personally experienced this sort of issue in maybe 10 years.


You can't exaclty "downgrade". You habe to create a bootable drive with your installer, boot from that drive, reformat your internal (backup first!) and then install 10.7

Make sure your computer supports it first.


In my opinion some more infos would be great to help you:

  1. What do you mean with "Mavericks Developer installed already"? Does it mean it is a beta Mavericks installation only available for developers? Or do you mean XCode is installed?
  2. Why do you want to downgrade to 10.7?
  3. "and other things don't work": what is not working? I do not see the connection.
  4. Why do you want "to keep all user profiles and software intact"? You bought a second hand iMac, and I would expect that you would like to reset it.

A little hint for users who sell their computer: you should re-install the Mac system and remove all data before selling you computer!

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