Macintosh: Troubleshooting a Rejected Disk
I keep getting a message saying, "This is not a Macintosh disk: Do you want to initialize it?" or "This disk is damaged: Do you want to initialize it?"I know the disk had already been formatted for a Macintosh and I have not had problems with it before. What is wrong now?
When you get these messages and you are certain the disk is properly formatted, click No. If you click Yes, all the data on the disk is overwritten by the Macintosh and lost.
Immediately lock the disk. This protects your data in case the problem is a damaged directory or misaligned drive; both of these problems can cause your data to be erased from an unlocked disk.
What to Look For
If you are using a Macintosh Quadra 660AV or Quadra 840AV, your disks could be rejected because these models use a different floppy disk controller which reads and writes data more precisely than the one in most other Macintosh computers. It may not be able to read your disk, especially if it was manufactured by a mass-duplication process. If this occurs with software installation floppy disks, contact the vendor for another copy of the software.
NOTE: This problem can occur if composite SIMMs are installed in your machine. Confirm that any additional RAM added is non-composite. Apple only supports non-composite SIMMs. If you are not sure whether you have composite SIMMs, read the Technical Information Library article titled, "Composite SIMMs: How to Identify."
1.4 MB High-Density Disks
If the disk is a 1.4 MB high-density disk and the drive can only read 400K or 800K disks (Macintosh computers before and including the Macintosh Plus, the original Macintosh II models, and some Macintosh SE models), it cannot be read by anything other than a SuperDrive (FDHD, or floppy drive, high density).
High-Density Disks
If the disk is a high-density disk that was formatted as an 800K disk, your drive gives you a message like "This disk is improperly formatted for this drive. Do you want to initialize it?"
The best option in this case is to remove the disk and reinsert it in an 800K drive. However, if no 800K drive is available, you can trick the drive by putting tape over the hole in the upper-left corner of the disk (be sure to cover both sides of the hole).
Save any information you need from the disk onto the hard drive, eject the disk, remove the tape, and reformat the disk as soon as possible.
NOTE: Use this technique only for emergencies.
Putting tape or any other item that could come off in the floppy drive can damage your computer.
Try the disk in another drive
If it works properly, this may indicate that one of the drives is misaligned or broken. When a disk that was written on by one drive cannot be read by another, the heads on one of the drives is out of alignment. The drive that is misaligned or broken may not be the drive that cannot read the disk; try the disk in three or four drives to identify the drive with the problem.
Warm or Cold Disks
If the disk is too warm or too cold, the drive may not be able to read it properly.
You can warm up a cold disk safely by setting it on top of your monitor for a few minutes. An overly warm disk can be cooled by placing it in a shady, cool place. DO NOT attempt to heat or cool a disk in an oven or refrigerator.
Damaged Disks
If none of these resolves or identifies the problem, the disk is damaged. You can attempt to make a copy of unreadable or damaged disks using a disk recovery software program (like MacTools FastCopy by Central Point Software), then try fixing the problem using a repair utility.
The first utility to try would be Disk First Aid which is included on one of the System disks (Utilities or Disk Tools) that came with your Macintosh computer. If it does not completely repair the problem, try running Disk First Aid several times. If Disk First Aid cannot fix the problem, there are many other recovery utilities you can try.
Other repair or recovery utilities may do more complex repairs than Disk First Aid. You might try one of these utilities for severely damaged disks. You might at least be able recover some of your data. Some examples of these utilities include Norton Utilities by Symantec or MacTools Deluxe by Central Point Software.
Other Disk Formats
If you are using MS-DOS or ProDOS formatted disks, you must have the PC Exchange control panel installed and have a High-Density drive installed in your Macintosh computer. While your macintosh computer can read both ProDOS and MS-DOS disks, you should still use only Macintosh formatted disks if you are not exchanging files between Apple II or MS-DOS computers.
There is an additional step you may have to perform if you are using MS-DOS or ProDOS formatted floppies. You may have to throw away the PC Exchange Preferences file. It is located in the Preferences folder within the System Folder. If this file has become damaged, you may no longer be able to mount MS-DOS and ProDOS formatted disks. Once you have removed the PC Exchange Preferences file, a new one is created the next time you start your computer.
This article provides information about some non-Apple products. Apple Computer, Inc. is not responsible for its content. Please contact the vendor for additional information.
The Tech Info Library article titled "Locating Vendor Information" can help you search for a particular vendor's address and phone number.
Immediately lock the disk. This protects your data in case the problem is a damaged directory or misaligned drive; both of these problems can cause your data to be erased from an unlocked disk.
What to Look For
If you are using a Macintosh Quadra 660AV or Quadra 840AV, your disks could be rejected because these models use a different floppy disk controller which reads and writes data more precisely than the one in most other Macintosh computers. It may not be able to read your disk, especially if it was manufactured by a mass-duplication process. If this occurs with software installation floppy disks, contact the vendor for another copy of the software.
NOTE: This problem can occur if composite SIMMs are installed in your machine. Confirm that any additional RAM added is non-composite. Apple only supports non-composite SIMMs. If you are not sure whether you have composite SIMMs, read the Technical Information Library article titled, "Composite SIMMs: How to Identify."
1.4 MB High-Density Disks
If the disk is a 1.4 MB high-density disk and the drive can only read 400K or 800K disks (Macintosh computers before and including the Macintosh Plus, the original Macintosh II models, and some Macintosh SE models), it cannot be read by anything other than a SuperDrive (FDHD, or floppy drive, high density).
High-Density Disks
If the disk is a high-density disk that was formatted as an 800K disk, your drive gives you a message like "This disk is improperly formatted for this drive. Do you want to initialize it?"
The best option in this case is to remove the disk and reinsert it in an 800K drive. However, if no 800K drive is available, you can trick the drive by putting tape over the hole in the upper-left corner of the disk (be sure to cover both sides of the hole).
Save any information you need from the disk onto the hard drive, eject the disk, remove the tape, and reformat the disk as soon as possible.
NOTE: Use this technique only for emergencies.
Putting tape or any other item that could come off in the floppy drive can damage your computer.
Try the disk in another drive
If it works properly, this may indicate that one of the drives is misaligned or broken. When a disk that was written on by one drive cannot be read by another, the heads on one of the drives is out of alignment. The drive that is misaligned or broken may not be the drive that cannot read the disk; try the disk in three or four drives to identify the drive with the problem.
Warm or Cold Disks
If the disk is too warm or too cold, the drive may not be able to read it properly.
You can warm up a cold disk safely by setting it on top of your monitor for a few minutes. An overly warm disk can be cooled by placing it in a shady, cool place. DO NOT attempt to heat or cool a disk in an oven or refrigerator.
Damaged Disks
If none of these resolves or identifies the problem, the disk is damaged. You can attempt to make a copy of unreadable or damaged disks using a disk recovery software program (like MacTools FastCopy by Central Point Software), then try fixing the problem using a repair utility.
The first utility to try would be Disk First Aid which is included on one of the System disks (Utilities or Disk Tools) that came with your Macintosh computer. If it does not completely repair the problem, try running Disk First Aid several times. If Disk First Aid cannot fix the problem, there are many other recovery utilities you can try.
Other repair or recovery utilities may do more complex repairs than Disk First Aid. You might try one of these utilities for severely damaged disks. You might at least be able recover some of your data. Some examples of these utilities include Norton Utilities by Symantec or MacTools Deluxe by Central Point Software.
Other Disk Formats
If you are using MS-DOS or ProDOS formatted disks, you must have the PC Exchange control panel installed and have a High-Density drive installed in your Macintosh computer. While your macintosh computer can read both ProDOS and MS-DOS disks, you should still use only Macintosh formatted disks if you are not exchanging files between Apple II or MS-DOS computers.
There is an additional step you may have to perform if you are using MS-DOS or ProDOS formatted floppies. You may have to throw away the PC Exchange Preferences file. It is located in the Preferences folder within the System Folder. If this file has become damaged, you may no longer be able to mount MS-DOS and ProDOS formatted disks. Once you have removed the PC Exchange Preferences file, a new one is created the next time you start your computer.
This article provides information about some non-Apple products. Apple Computer, Inc. is not responsible for its content. Please contact the vendor for additional information.
The Tech Info Library article titled "Locating Vendor Information" can help you search for a particular vendor's address and phone number.