Is There Anything I Should Do or Know Prior to Reinstalling an Operating System?

You cannot reinstall an earlier version of Mac OS X over a later version unless you perform an archive install or reformat the computer.

Read the "Before You Install" or "Read Me" document associated with your operating system if one is available for the software you are installing. This may list the system requirements and any known problems.
If you receive a warning message about updating your computer's firmware, be sure to do so prior to installing the operating system. For the latest Firmware Updates, go to the Apple Downloads Web page.
Allocate a couple of hours or more to reinstall Mac OS X, software updates, and your application software.
Back up all important documents to a separate device before beginning.
Have all application software disks or CDs readily available for reinstalling if you plan to do a reformat/reinstallation of Mac OS X. This involves deleting all files on your hard drive and copying an entirely new set of operating system files on to your computer. This replaces the previous operating system, and is preferred in general, as it will most likely eliminate previous system software problems. In contrast, an archive install moves all older operating system files into a new folder called Previous System Folder. It keeps your data intact but you will need to manually move preferences.

08/13/08