OS X Mountain Lion requires a Mac with a 64-bit kernel. Mountain Lion supports the following Mac models:
• iMac (mid 2007 or later)
• MacBook (13-inch Aluminum, 2008), (13-inch, Early 2009 or later)
• MacBook Pro (13-inch, Mid-2009 or later), (15-inch, 2.4/2.2 GHz), (17-inch, Late 2007 or later)
• MacBook Air (Late 2008 or later)
• Mac Mini (Early 2009 or later)
• Mac Pro (Early 2008 or later)
• Xserve (Early 2009)
Download Mountain Lion DP1 from here or wherever you like.
Make sure you have enough space on your hard drive and create a NEW PARTITION formatted as Mac OS X Extended (Journaled). We will use this as TARGET PARTITION.
Mount Mountain Lion DP1 and proceed with the installation. When you have to select the targetdisk/partition, click on “show all” and select the partition you created at step 2. Will install for several minutes (around six) then it will restart.
When restarting the installation will continue for about half an hour. Wait… And wait…
You now have Mountain Lion on a separate partition and you won’t lose your files, configuration, applications. Feel free to play with it as much as you want.
by Karmic Alice (Amy Mem)