Every Mac computer comes with a copy of the operating system that is installed on it. For Macs running on a version of OS X, you will have the version of OS X your Mac came with originally. If you ever need to troubleshoot your Mac, the OS X disks will become invaluable. In order to make sure the disks are kept safe you can make a bootable backup copy of them using Disk Utility to make the DVD into an ISO and then burn it to another DVD.
Insert the Mac OS X Install DVD into your Mac’s optical drive.
Open Disk Utility on your Mac. It is in the “Utilities” Folder in the Application’s folder or the Finder’s “Go” menu.
Click on the Mac OS X Install DVD on the left hand side of the Disk Utilities window and select “New Image” from the menu bar. Name the ISO, choose a location and keep the format and encryption in their default modes.
Click “Save.” Eject the Mac OS X Install DVD when it is done making the ISO. Do not mount the ISO.
Click “Burn” in the upper left hand side of the Disk Utility window. Insert a DVD-R into your Mac’s optical drive. Choose “1x” for the burn speed and click “Burn.”