I have an external hard drive that I've used with my Mac for years, with no issues. Today I tried to plug it into my work PC to get some files off it (Windows 8), and it wasn't recognized. I tried to look up how to reformat it, but realized it was going to delete my files. So, I decided to forget that idea and plugged it back into my Mac. Now, it won't run, and Disk Utility says that the Partition Type is Microsoft Reserved.

It won't let me repair or verify in the Disk Utility because it says "ERROR: Partition map check failed because no slices were found."

Now, I can't access my files on either computer, which has like my life's worth of photos on it. I am about to have a heart attack if I've lost all of my data! I've been searching online and have seen many things where it says to create new partitions, but from what I understand that will delete all the data on the existing drive, which I don't want to do because I obviously don't have it backed up anywhere else (because this external hard drive WAS my backup).

Please, someone out there help me!!

MacBook Pro, OS X Yosemite (10.10.3)

  • A second UGH - if your backup is the only copy, it needs a backup going forward. Sorry for the answer to get help, but you are reading the warnings correctly - the normal tools are going to erase the drive and make data recovery harder so it's good that you stopped to ask for help at this point.
    – bmike
    Nov 29, 2015 at 16:30
  • Please open Terminal.app and enter diskutil list and hit the enter key. Determine the disk identifier of your external disk. Use the disk identifier in sudo gpt -r show /dev/diskX and hit enter again. Replace diskX with the disk identifier found earlier (probably disk1). Add the result to your question by editing it.
    – klanomath
    Nov 29, 2015 at 17:02

1 Answer 1


Ugh - the main thing with "your life's work of photos" is to slow down and don't panic. Don't try to fix things when you're desperate or rushed. Don't try something for the first time on that drive. The normal utilities exist to make the drive usable at the expense of losing your files. Or if the files are "lost" not, then at the expense of letting recovery software get some or all of them back.

Instead, reach out to your network of friends to see if anyone has used a program like Data Rescue to repair/recover deleted files. Learn how to connect a drive in read-only mode (you might need to buy hardware or take the drive to someone that does this professionally or has at least gotten three successful recoveries under their belt before you entrust your only copy of your work with them).

You might have lost the photos, but I wouldn't recommend connecting the drive to either a PC or a Mac since both will try to run filesystem checks and if the part of the drive that tells either OS what is on the drive itself is corrupt or just not making sense, that computer could do more damage to your work trying to make the drive "usable" again.

The reason I recommend having a partner is that you will then work together, slow down and be intentional about what steps you take. Just explaining what you are about to do is valuable even if the partner isn't experienced in data recovery.

  • Thank you all, will try some of these suggestions and let you know.
    – Liz
    Nov 30, 2015 at 3:53
  • @Liz OK - best luck that this works!
    – bmike
    Dec 8, 2017 at 22:32

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .