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)