Install & boot Mac OSX on an external hard drive Need MAC OS to install the external storage device. Create a disk image on the desktop. Use Disk utility, utility application, disk utility, MAC OS install DVD new image. Choose Image format, DVD/CD master. Leave encryption at none. Partition and name the external drive. Name one partition Install and the other Leopard 2. Save. Partition the drive. Make two partitions and save to the desktop. Choose disk utility install-restore. Source is the final destination image. Destination is the install partition. Hit restore twice. Enter you password. Restart the computer and hold down the option key. There are two hard drives. Choose install. Select Leopard 2. Install. Reboot. Hold option key. Select Leopard 2. Computer will request standard set up information.