If you are looking to install or re-install Mac OS X onto a computer that does not have a native DVD drive (such as the Macbook Air) or a broken drive, you can use a very cheap USB thumb drive to install it.
The requirements for the external drive must be at least 8 gigs but those can be found for $10-20 dollars on the right deal!? Plus you can easily wipe the drive after to use it for file storage.
1.? Connect your external thumb drive or hard drive to your computer and let it appear as a connected drive on your desktop.
2.? Pop in the Mac OS X disk into your DVD drive.
3.? Open Disk Utility and select the external hard drive on the top left.
4. On the main window, look for the restore tab.? There will be a field for a Source image.
5.? On the left side, drag over the Mac OS X disk into the Source and your external device into the destination field.
6.? Verify both paths are correct and then click on restore- it may take some time to finish this step.
7.? Once this is complete, you can click on the Startup Disk icon in System Preferences, and click on the external source that Leopard was installed on.? It will reboot the computer and start the installation from your USB source!