I had Leopard on may Mac. I upgraded to Mountain Lion using Snow Leopard. I can't use my video with Mountain Lion. Can I load Snow Leopard on an external hard drive so I can use it with my camera?

Question

I had Leopard on may Mac. I upgraded to Mountain Lion using Snow Leopard. I can't use my video with Mountain Lion. Can I load Snow Leopard on an external hard drive so I can use it with my camera?

Answer 1

First, you cannot do this if you have a Boot Camp partition.
Second: Create a new partition.
1. Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
After the main menu appears select Disk Utility and click on the Continue button. Select the hard drive's main entry then click on the Partition tab in the DU main window.
2. You should see the graphical sizing window showing the existing partitions. A portion may appear as a blue rectangle representing the used space on a partition.
3. In the lower right corner of the sizing rectangle for each partition is a resizing gadget. Select it with the mouse and move the bottom of the rectangle upwards until you have reduced the existing partition enough to create the desired new volume's size. The space below the resized partition will appear gray. Click on the Apply button and wait until the process has completed.  (Note: You can only make a partition smaller in order to create new free space.)
4. Click on the [+] button below the sizing window to add a new partition in the gray space you freed up. Give the new volume a name, if you wish, then click on the Apply button. Wait until the process has completed.
You should now have a new volume on the drive.
It would be wise to have a backup of your current system as resizing is not necessarily free of risk for data loss.  Your drive must have sufficient contiguous free space for this process to work.
Third: Install Snow Leopard.
Boot from your Snow Leopard DVD. Follow instructions for installation being sure that before you actually install Snow Leopard you have selected the new partition as your target destination.
Booting From An OS X Installer Disc
  1. Insert OS X Installer Disc into the optical drive.
  2. Restart the computer.
  3. Immediately after the chime press and hold down the "C" key.
  4. Release the key when the spinning gear below the dark gray Apple logo
      appears.
  5. Wait for installer to finish loading.