Don't install a version of Mac OS X earlier than that which came with your Mac
Summary
Both PowerPC- and Intel-based Macs have with a certain version of Mac OS on their installation disc(s). If you install an earlier (previous) version of the Mac OS 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
An alert message may appear during installation stating that you are using an incorrect disc.
Products Affected
Mac OS X 10.4, Mac OS X 10.3, Mac OS X 10.2, Mac OS X 10.1, Mac OS X 10.0, Mac OS X 10.5, Mac OS X 10.6, Mac OS installation/setup (any version)
If an alert message appears stating you are using an incorrect disc, you should not 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). Consult the User Guide that came with your computer for more information.
Additional Information
Important: Even though one version of system software may be identical in version number to another, the software may not be exactly the same. For example, you may have a retail version of the Leopard install disc (Mac OS X v10.5) and your computer perhaps came with Mac OS X v10.5. Your computer may have additional software specific to it included on its software disc (Mac OS X 10.5) which may not be present on the retail Mac OS X v10.5 disc. See this article for more information.
Be sure to use the original software discs that came with your computer when performing a reinstall of Mac OS X unless you are installing a new release (for example, installing the retail version of Mac OS X 10.5 onto a compatible Mac that shipped with Mac OS X 10.4 is fine). This is particularly important if you are creating and installing custom disc images.