The inexpensive OS 8.5 CDs which say "iMac", "iBook" and "PowerMac G3" on them contain SYSTEM-SPECIFIC software installations and were meant for only the particular Macintosh they were sold with. They install some software components that your Mac cannot use or doesn't need. Many times, the OS software won't even install on your Mac. We sell the universal general-installation OS 8.5 CDs which do not specify a particular machine. They are meant for ANY Macintosh that supports OS 8.5 and will install an appropriate version on your machine. Before you buy from another source, make sure you know what CD you are getting. No matter what the seller says about them, system-specific versions have caused problems when used on other computer models. This is why they sell for less than the universal installers. Apple considers it a violation of their software license agreement when operating systems from system-specific CDs are installed on machines other than the ones for which they were intended.