I have a Macbook Pro with an SSD drive installed. The laptop runs OS X 10.11 (El Capitan) and Windows 7 on a Bootcamp partition. Something weird was going on however. The drive itself is 512GB, but the only partitions I could see in OSX where a 170GB Macintosh HD and a 90GB BOOTCAMP.

When booting in Windows, I saw there was about 200GB of 'unused' space. I created a partition in Windows and formatted it. All good.

After rebooting, however, my Macintosh HD disappeared and the Windows partition boots, but doesn't get to the login screen (instead it goes to recovery mode).

My feeling is that Windows replaced the GUID partition map with an MBR one, which essentially makes partitions unmountable. OS X still recognizes the partition layout, however, as can be seen in the screenshot below:

Disk Utility

Is there any way to recover the original partition map?

  • "created a partition in Windows and formatted it. All good." ... no, not all good. Golden Rule: never allow Windows to touch the partitions. It doesn't understand how it's being fooled into thinking it's in charge. – Tetsujin Oct 1 '16 at 12:15
  • Please add the outputs of diskutil list, sudo gpt -r show disk3 and finally sudo fdisk /dev/disk3 to your question! The screenshot of Disk Utility is not helpful at all (though I can read dutch a lil' bit). You may have to apply the disk identifier (i.e now disk3) according to the listing of the first command because it may change after un/replugging the external usb drive. Also add your Mac model (e.g MacBookPro11,2). – klanomath Oct 1 '16 at 12:52

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