Select the new Mac OS X Install ESD partition that appears then click the Restore tab. Right click or control-click the InstallESD.dmg image from the left side of Disk Utility and choose Open Disk Image from the popup. When asked to confirm click the Partition button. Next click the Apply button to save your changes. Set the Partition Layout to 1 Partition, set the Name to 'MOUNTAINLION', set the Format to Mac OS Extended (Journaled), and then click the Options button.Ĭhoose GUID Partition Table from the popup window then click the OK button. Select your USB thumb drive from the list on the left and click the Partition tab. Right click or 'Control' click InstallESD.dmg and select Disk Utility from the Open With menu. Then double click the SharedSupport folder Navigate to the Applications folder and right click the new 'Install OS X Mountain Lion' icon then select Show Package Contents from the contextual menu. Select Quit from the Install Mac OS X Lion to exit the installer.Ĭlick to launch a new Finder window from your dock. Once the download has completed the Mac OS X Lion Installer will launch.

If the LaunchPad appears press the Escape key.

Press the Install button for OS X Mountain Lion and wait while the operating system downloads. **If you have not yet installed Mountain Lion then you can follow these instructions to buy it and begin downloading.

Mac os mountain lion bootable usb