Because of the ".AppleCD" driver which is installed in the System Folder on most Power Macintosh system software CD-ROM discs it is possible for these discs to mount on the desktop even if you startup your Power Macintosh computer with all extensions off. (You can turn all extensions off by pressing and holding the Shift key during startup.) Most CD-ROM discs, other than Apple system software discs, do not mount on the desktop if extensions are off because the Apple CD-ROM extension on the computer's hard drive is not loaded at startup. If the system software disc which is in the drive when you startup with extensions off is the disc that came with that model, it causes no problems and can easily be ejected in a normal manner.

There have been some instances when customers have started up their PCI-based Power Macintosh computer with extensions off and found that they had left a system software CD-ROM disc for an older Power Macintosh model in the CD-ROM drive. This CD-ROM disc will show up on the desktop because of the special extension on the CD. However, when you attempt to eject this CD-ROM disc, you get a -50 error message.

During the startup process, the computer checks all available SCSI volumes, including the CD-ROM drive. If the CD-ROM disc contains the ".AppleCD" driver, it will be loaded and used by the computer to access the CD-ROM drive in lieu of the CD-ROM software that would have loaded if the extensions were not off. This works fine for most purposes.

However, the PCI-based Power Macintosh computers (Power Macintosh 7200, 7500, 8500, and 9500 series) need slightly different information than previous Power Macintosh computers to eject the CD-ROM disc. This causes the -50 error which indicates that the internal parameters being used to eject the CD are incorrect. You can eject the CD-ROM disc if you restart the computer again with extensions enabled.

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