I'm helping a friend repair his 2012 13" MBP. Initially I tried to reinstall everything on the old hard drive but it looked like the old hard drive had failed (couldn't reformat it in Disk Utility on a Yosemite Installer USB) I had a 500GB HGST drive from an old Lenovo which has OPAL (basically you can enable hardware encryption, but I don't believe it was enabled). I put this drive in place of the old one and the OS X installer refused to recognize it (did not show up in list of disks at all). Then I booted up GParted and it would recognize the disk fine. So then I put the drive in a USB-SATA enclosure, loaded up the OS X installer again and voila... the installer could recognize and format the drive totally fine through USB. I formatted it to HFS+ journaled and installed Yosemite on it. It booted up fine and everything (from USB), but when I put the drive back in the machine (SATA), it couldn't find it again. I initially thought it was the SATA cable that was broken (looks like a common problem) but I also tried putting in an old Seagate 120GB drive and that thing worked flawlessly. So I'm guessing it's something to do with this specific 500GB drive. I'd put in the 120gb and call it a day but it's not enough space. Anyone run into any similar issues?