MacPostfactor is a tool to install Mac OSX 10.8+ on older Macbooks that normally only support up to OSX 10.7 (Lion). It works through a combination of a highly customized installer, a replaced set of drivers and various frameworks, and the original installation app from the App Store. The installation can be done directly on a Macbook already running OSX Lion (so no USB disk required), or on an USB media for installation on another system.

Requirements

• You need an Intel-based Macbook capable of running OSX Lion (10.7) (otherwise your Mac is too old), but one that does not support OSX Mountain Lion (10.8) or higher. PowerPC-based Macs are not supported (they do not run OSX Lion).
• The installer app of the OSX version to install, from the App Store.

No particular or in-depth knowledge of Mac or OSX is required to use this. The installation can be done directly on a working Mac that's running OSX Lion (10.7).

Warning

Do not use MacPostFactor to install OSX on a system that officially supports newer OSX versions. Doing so will most likely make your system unbootable.

Download

→ Official download link (from Mediafire).

Using MacPostFactor

Using MacPostFactor is very straight forward:

1. Retrieve the original installer app from the App Store. You may need to use another Mac that supports the version of OS X you want to install in order to be able to download the app directly from the App Store. See below for more tips on how to get the install app.
   Place the install app in the Applications. Otherwise MacPostFactor won't find it.
2. Dowload the installer, open the DMG and drag MacPostfactor in the Applications as well.
3. Start MacPostFactor and follow the on-screen instructions. The application will automatically determine which versions of OS X can be installed on your hardware. Choose the version of OSX you wish to install, and the disk/volume to install to. If you select to install to an external drive, the installer will create a bootable installation media, allowing you to perform an installation on another system. Selecting the volume on an internal drive will perform a clean install on that volume. You can select the currently active volume, which will then replace OSX Lion with whatever OSX version you choose.
   Keep in mind that 10.9 Mavericks and 10.10 Yosemite don't work properly on systems with an Intel GMA950 or X3100 graphics card, as there are no 64-bit drivers for those cards, and they do not properly support the newer OpenGL and OpenCL frameworks.
4. The installer will perform some tests, verifying your Mac is capable of running the selected OSX version. When that's done, the installation will continue. It will take some time for this to complete.
5. When the installation has succesfully completed, you will be prompted to reboot. In case of an install to a local disk, you can restart the system to boot into the new system. You will then go through the first run wizard, like on a normal Mac.
   If you've done the installation to an external USB media, you can remove the media and use that to install the modified OSX version on another system.

Alternate ways of getting the install app

The only tricky part is to actually get the install app from the App Store of the OSX version you want to install. The App Store does not allow you to download the app on a Macbook that does not support it, so you'll have to be a bit creative.

You could use a Mac that supports the newer OSX versions and directly download the app from the App Store that way. It is not a problem if the OSX on that Mac is newer than the version you want to download. You'll get a warning but the download will continue. Once downloaded, you can then copy the app from the /Applications folder to another system, through network or USB.

If you use an USB media, it's best to "compress" the app before copying to ensure all files remain in place: right-click the app, then click Compress. This will create a ZIP file in the current folder.

Note that VMWare Fusion or Parallels supports newer OSX versions. Installing OSX as a virtual machine will also allow you to download the installer app from within that VM.