If you are useaing external hard drive and made an image of clone copy, but don’t have any dual layered disks lying around, you can always use an external hard drive to install Mac OS X 10.5 Leopard. This is incredibly easy, and works with both USB and Firewire hard drives:
1. Plug in your external hard drive
2. Open up Disk Utility
3. Click on the name of your external Hard disk
4. Click on the “Restore” tab
5. In the “Source” field, select the image file (such as leopard.dmg) from wherever it is on your hard drive
6. In the “Destination” field, drag your external hard drive from the Disk Utility drive list on the left onto this field. Of course, if it’s only a partition on the external drive that you want to use, drag only the partition.
Note: anything on the partition will be erased and replaced with the installation files for Leopard. Therefore, it is best to make a partition on the external hard drive which has about 8 gigabytes. Use this partition as the destination so that everything else on the drive remains unchanged.
7. Click on restore. This may take awhile.
8. Once its done, open up System Preferences
9. Click on Startup Disk
10. Select the external hard drive (or partition in it) with the Leopard Install
11. Click Restart. The leopard installation will begin from the external hard drive. This installation is identical to installing leopard with a DVD.