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August 12, 2012

How to install OS X Mountain Lion on a MBR partition with Unibeast

When you install Windows on a hard drive, it automatically sets the partition scheme of your hard disk to MBR (Master Boot Record). Mac OS X doesn't support this partition scheme, but you can still install OS X Mountain Lion on a hard disk with the MBR partition scheme by modifying "OSInstall.mpkg" and "OSInstall", two installation files inside your Unibeast USB drive. This means that you can install Mac OS X on a hard drive that already has Windows installed.

NOTE: You can apply this guide's method to the Kakewalk tool, with the same effect. The myHack tool and the iAtkos distro automatically apply the MBR patch when installing OS X Mountain Lion. This guide cannot be applied to Niresh's distro, which is distributed as an ISO file (and therefore cannot be written onto).

  • A compatible computer: Not every computer will work with Mac OS X, even with the help of tools like Unibeast and Multibeast. Be sure to read the Hackintosh compatibility guide very carefully, to check whether or not your computer qualifies. The hardware requirements for OS X Mountain Lion are essentially identical to those for Mac OS X Lion; AMD processors and older 32-bit Intel processors (such as Pentium M) are not supported.

  • A hard drive with at least 10 GB of free space: OS X Mountain Lion takes up about 7 GB of space on its initial installation. Therefore, the computer where you install Mac OS X must have enough space in its hard drive. However, 10 GB is only the bare minimum; if you plan to install Mac OS X for day-to-day use, I recommend allocating at least 50 GB of space.

  • Unibeast (Free): Unibeast is a Mac program that modifies the official OS X Mountain Lion installer, and writes it onto a USB drive. You can then use this Unibeast USB drive to run the Mountain Lion installer on a PC. Unibeast works with Mac OS X Snow Leopard and newer; registration on is required to download Unibeast. 

  • A Hackintosh with Snow Leopard/Lion already installed, a real Mac, or a Mac OS X virtual machineUnibeast is a Mac app, so you need a computer with Mac OS X to run it. You could use a real Mac, if you own one. Alternatively, you could install Mac OS X Snow Leopard on your PC, and then follow this guide to update your PC to Mountain Lion (if your computer uses an Ivy Bridge processor, be sure to use iBoot for Ivy Bridge).

    As one last option, you could install Snow Leopard on a virtual machine, and run Unibeast on there instead. Be sure to install the Virtualbox Extension Pack to view USB drives from your virtual machineThis method will probably not work if your computer uses an Ivy Bridge processor (though I haven't personally confirmed this).

  • OS X Mountain Lion ($20): The method used by this guide requires that you have a copy of the Mountain Lion installer app ($20) from the Mac App Store. Though the Mac App Store is included in Mac OS X 10.6.6 and newer, you have to be running 10.6.8 to download Mountain Lion. (you might be able to circumvent this requirement by spoofing your system version).

  • An empty USB drive (8 GB or larger): The USB drive used for Unibeast must be at least 8 GB in size. Since Unibeast will erase all of the files on your USB drive, make sure to back up its contents first. You can reuse this USB drive for normal stuff after you finish installing Mountain Lion.

  • Multibeast (Free): Multibeast is a collection of kext files that your Hackintosh will need to run properly, after the initial installation. Download it onto a USB drive. Be sure to download the newest version, not the older version 3 of Multibeast, which is for Snow Leopard.

  • A modified version of OSInstall.mpkg and OSInstall framework (Free): These two OSInstall files stop the OS X Mountain Lion installer app from checking whether your hard drive has the MBR partition scheme.

    Every version of the OS X Mountain Lion installer app requires a slightly different version of these two files. As of the writing of this guide, Mountain Lion is on its first public version (10.8.0), so you need to use the 10.8.0 GM versions of the OSInstall files. "GM" stands for Gold Master, the final beta version of Mountain Lion before it was released to the public; it is exactly identical to the public version of 10.8.0.

1. Create a hard drive partition for Mac OS X
Boot into Windows Vista or Windows 7, and type "partition" into your Start Menu search bar. Choose "Create and Format hard drive partitions" to open the Disk Management utility in Windows.

You will see a bar displaying the partitions in your hard drive. Right-click on the emptiest partition in the hard drive that you want to install OS X on, and click "Shrink". This will allow you to shrink the size of that partition, so that you have extra space on your hard drive to create a new partition for Mac OS X.

Once the shrinking process is complete, you should now have some unallocated on your hard drive. Right-click the Unallocated section of your hard drive's bar, and choose "New Simple Volume".

A helper will pop up. From here, format the Unallocated space as a NTFS volume (or an exFAT volume; it shouldn't matter, since you'll be wiping this partition in OS X anyways).

2. Run Unibeast
After you've set up your MBR hard disk, boot into Mac OS X (either on your existing Hackintosh or on your real Mac) and run Unibeast on your USB drive. Check out Steps 1-2 of our Mountain Lion installation guide for more details.

3. Replace the OSInstall files
This is the really important part. By principle, Unibeast modifies as few files in the standard Mountain Lion installer app as possible. However, this means that you won't be able to install Mountain Lion on a hard disk with the MBR partition scheme without doing some hackwork of your own.

After downloading copies of OSInstall.mpkg and OSInstall for your version of the Lion installer app, enable viewing of hidden files on Mac OS X. Then open your Unibeast USB drive from Mac OS X. It should look like this.

Go to System/Installation/Packages inside the Unibeast USB drive and delete the file "OSInstall.mpkg".

If you haven't already, double-click on the ZIP file that you downloaded with the OSInstall files inside (check the "Requirements" section at the top of this guide for download links). A folder will be extracted; inside the folder are the modified versions of OSInstall.mpkg and OSInstall.

Find the new version of OSInstall.mpkg from the unzipped "System" folder that you downloaded. Copy this version of OSInstall.mpkg into the "Packages" folder in your Unibeast USB drive.

Then, go to the following location inside your Unibeast USB drive:


NOTE: In OS X Yosemite, the file location has changed slightly, to the following:


Delete the OSInstall file inside this "A" folder.

Next, find the modified version of the OSInstall file, from the unzipped folder that you previously downloaded. Copy this OSInstall file into the "A" folder on your Unibeast USB drive.

4. Install OS X Mountain Lion
Next, you'll need to set the appropriate BIOS settings for your computer, and then actually install OS X Mountain Lion. Check out Steps 3-7 on our Mountain Lion installation guide for more details.

Once that's done with, you should be running a fully functional copy of OS X Mountain Lion on your PC. Congratulations!