Okay so, I have a mac and a windows and I recently got an external hard disc. So I put my mom's iphone pictures on the external hard disc through my mac. (I created a partition/ formatted). Then I plugged the external hard disc to my windows pc and realized that the external hard disc didn't show up on my windows pc(I didn't know that mac and windows couldn't share external hard disc). So I formatted it on my windows pc, and then I plugged it back to my mac and my files were gone. I probably sound really stupid, but I don't know what to do I thought I created one "thing" for mac and one for windows.