Don't install a version of Mac OS X earlier than what came with your Mac

Both PowerPC- and Intel-based Macs ship with a certain version of Mac OS X (or Mac OS X Server) on their installation disc(s). You should not install a version of Mac OS X earlier than that which came with your Mac.

If you install an earlier (previous) version of the Mac OS X than what was included, your computer may exhibit unexpected behavior such as:

• The trackpad or mouse may not respond properly
• The computer may stop responding
• Sleep/wake issues may occur
• The display image may appear to "shrink" with black bars around it, may appear tinted, or have other issues
• Loss of built-in audio
• Loss of Bluetooth or AirPort functionality
• May not start up past the Apple logo

See this article to learn if the Mac OS X or Mac OS X Server version on your Mac is what originally came with the computer.

If you are installing an earlier Mac OS X version from a disc

If an alert message appears stating you are using an incorrect disc, then you should not try to use that disc with your Mac.

If you already installed a previous version of Mac OS X and are having issues with your computer, you should reinstall Mac OS X with the installation disc(s) that came with your Mac (or use installation discs containing a later, compatible version of Mac OS X or Mac OS X Server). Consult the user guide that came with your computer for more information.

If you are trying to restore a Time Machine backup that was made on a different Mac

If you receive an alert message that your Time Machine backup is from an older Mac OS X version (or if you already know your Time Machine backup is from a different Mac that's using an earlier Mac OS X version than what came with your Mac) you should use Migration Assistant to move your information over instead of restoring. See the "Restoring your entire system from a backup" section of this article.

With Mac OS X v10.6.3 and later, if you attempt to restore a Time Machine backup that was created on a different Mac, you may receive this alert: "You can't restore this backup because it was created by a different model of Mac". See the "Restoring your entire system from a backup" section of this article.