CD-ROM: "This disk is unreadable" Message

Hi, zunigae -

Welcome to Apple's Discussions.

Several items in the Extensions folder do not appear in Extensions Manager, apparently by design.

One important one of this type is the extension named Text Encoding Converter. This is done to prevent it from being disabled accidentally.

The files "ISO 9660 File Access" and "Audio CD Access" apparently are not shown because they do nothing as stand-alone files; they are used solely by AppleCD/DVD Driver.

Any/all files present in the Extensions folder at the time of booting are active, whether or not they are shown in Extensions Manager. That is why it is usually necessary to reboot/restart the machine in order to make any changes to the array of extensions active.

All that Extensions Manager does is to move files; it does not authorize any of them.

When you uncheck an extension, Extensions Manager moves it into the Extensions (disabled) folder; when you checkmark one, Extensions Manager moves it into the Extensions folder. Extensions Manaager also maintains a list, a sort of registry, of what files were last placed where; this is how it is able to notify you that an extension it thought should be active is now missing (which is what happens when you manaually remove a file from the Extensions folder).

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Things that can interfere with the ability to read CDs -

• In some OS 9 configs, Toast's "CD Reader" extension can interfere. If that one is present, try disabling it and restarting.

• A dirty drive. Sometimes the lenses in a drive can collect sufficient dust or dirt that they no longer function adequately. The solution for that is to try using an audio CD player's cleaning disk.

• A defective drive. An optical drive can fail. One way to test for that is to try booting the machine to a known-good OS Install CD, one valid for that machine model. Since booting to a CD eliminates the use (hence potential interference) of any software on the hard drive, it is a good way to test to see if the probable source of a problem is software or hardware.

An external USB CD reader will not be bootable, so it only addresses part of the problem. The "real" solution is to replace the drive.

Replacing the CD drive requires some disassembly. On that model it is complex, but not dangerous, as the CRT section is not exposed.

The iMac has USB ports. Any recommendations for an external USB CD/DVD drive

Something very inexpensive. For one, that computer very likely can only achieve USB1 speeds. You can use a USB2 enclosure (but can't get USB2 speeds), but if you're willing to accept a USB1 enclosure you can get one pretty much for free since nobody else wants them (e.g., I have one sitting in my box waiting for the next trip to the recycling facility). If you're lucky you can get an old enclosure with an old drive (hopefully still working) for nothing. Barring that, go for a free enclosure, then spend $30 for a new drive (Pioneer used to be recommended, though recently there have been posts about a drop in quality).

If you start looking at any solution costing more than $50 total you could be looking at just replacing the whole computer with a used G4.