How to Downgrade from the Mountain Lion Developer Preview to Lion

  1. Have a recent SuperDuper clone of the machine you want to downgrade created before installing Mountain Lion (the first machine).
  2. Have another computer currently running Lion (the second machine) and a USB drive of at least 8GB.
  3. Install and run the Lion Recovery Disk Assistant on the second machine.
  4. Boot the first machine from the USB stick created in the previous step.
  5. Launch Disk Utility.
  6. Restore the first machine’s hard drive using your SuperDuper clone by dragging the drives from the left hand pane to the Destination and Source fields,respectively, on the right.
  7. Stop trying to use development versions of operating systems as your primary operating system. Shit will break. Often badly.