# Partition Map Failed Because No Slices Were Found

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 '15 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 '15 at 17:02