Hey, Need any help or advice given. Gave a friend my external My Book 4TB Drive to get some files from it, and he said he couldn't get it to work. I know it was working beforehand on my machine which was running Mavericks. But since then I've updated to Yosemite and I learned he was on Yosemtie too. I have another 3TB drive and it works both on Yosemite with no issues. I just find it strange my newer drive, the 4tb doesn't work. Now when the drive is plugged it I get the following error message "the disk you inserted was not readable by this compute" with three options: initialise, ignore or eject. Any help or advice given is greatly appreciated.