I was able to download the ML installer application and installation was set up on a separate hard drive. I chose the MacPostFactor auto installation setting for ML and the computer restarts and promptly shuts down and restarts continually with an error message. The only way I could stop this from happening was to manually switch off my machine and remove the hard drive with ML partly set up on it before restarting in lion, repairing disk permissions and then replacing the drive. Needless to say I have not yet successfully installed ML. Is this a known issue and what is an alternative installation method or fix as I need ML to run programs that won't run in anything higher. System: Mac Pro 2.1 2x dp 2.66Ghz with 16Gb Ram running Lion on one drive and El Capitan on another.