I was attempting to install Windows 10 via Boot Camp on my late 2011 MBP (13", on 10.11.5). I have a dual-HD setup, where my main OS is on an SSD, and the conventional HD that came with my laptop is used for data. On the latter HD, I had a few partitions, one contained the original OS X (10.8) install (Macintosh HD), one had a Windows 8 install (BOOTCAMP), and the other I used for data, like music and games (because my SSD is only 128GB and I wanted to conserve it.) My intention with Boot Camp was to erase the Windows 8 partition and install Windows 10 in its place. My mistake was to try to use Apple's boot camp wizard. It screwed me over. After downloading the necessary drivers, it immediately restarted my machine and started booting from the DVD. For some reason, the install disc didn't boot up, so I booted back into OS X. I soon noticed that, on my "data" HD, instead of the 3 partitions I mentioned earlier, I only have one: "BOOTCAMP". The boot camp assistant formatted my drive, without asking or warning me. Now I have one big 750GB partition, apparently empty. How can I recover the data on this hard drive? I did not proceed with the Windows 10 install, so nothing should be overwritten right now. Thanks.