I recently purchased a 2012 iMac with Mountain Lion, I was previously using an older Mac 10.6.8 with Snow Leopard.
Not thinking about compatibility, I plugged my WD external backup drive into new computer. When doing so, it said that I have approximately 1.2 TB free space out of 2TB. I started to do a backup on new computer, but stopped it immediately because of the amount of time it was going to require.
When trying to connect the external drive today, it would not and said 100% free space! Have all the files I had backed up on it from my old commuter been wiped out? I then reinserted that same external drive back into my old computer and received an error message that it does not recognize that drive.
Any suggestions? Could I have somehow wiped that drive when plugging it into new computer. I did not reformat.