MacBook – How to reclaim unoccupied disk space with Disk Utility

First I have to explain the gpt result:

The partition with index 1 is your EFI partition. The partitions with index 2 and 3 are your main OS X volume named Macintosh HD (also visible in the second screenshot) and your Recovery HD. The partition with the index 4 is your NTFS volume WinB (also visible in the second screenshot).

Trying to add a new partition (by using the +-button) or to resize Macintosh HD (by using the handle) with Disk Utility will downsize partition 2 and move partition 3 to the new end of partition 2.

Since adding a new partition with the +-button doesn't work properly for you, you have two options:

• use the handle and resize Macintosh HD. This should create unallocated free space

• or use the +-button and create a new volume. Apparently it will be formatted as a HFS+ Journaled volume.

  • Then boot to Internet Recovery Mode and open Terminal.
  • Enter diskutil list and gpt -r show /dev/disk0.
  • Unmount your main disk with diskutil umountDisk /dev/disk0.
  • Remove the new HFS+ volume with gpt and its index number found above:
    gpt remove -i 4 disk0
  • Enter exit and quit Terminal
  • Reboot

This might break Boot Camp as stated in Disk Utility and is not recommended if Windows boots in MBR-mode. So backup your Mac (including the Bootcamp partition) first.

I tested this with a spare MacBook Air (Mid 2013 with a 250 GB SSD) and a vanilla Yosemite after installing Windows 8.1 R1. Regardless what I did, I had no problem to boot from either Windows 8.1 or OS X. Windows 8.1 seems to be booted in EFI-mode though.

Since you have an older Mac, Windows will probably be booted in hybrid MBR-mode. Adding a fourth partition (at position 3) will break bootability of the last one because only three partitions (and the EFI partition) are allowed.

Your EFI is missing in the partition table - the content should be still there though - and the Recovery HD's partition has the wrong type.

To salvage this you just have to rewrite the GUID partition table:

• Boot to Internet Recovery Mode
• Open Terminal in the menubar > Utilities > Terminal
• Enter diskutil list and with the disk identifier of the internal disk found there: gpt -r show diskX. Usually it's disk0 - below I assume it's disk0. Use the disk identifier you have found in your environment in the commands below!

• Unmount the internal disk:

  diskutil umountDisk /dev/disk0
  

• Remove all partitions:

  gpt remove -i 1 /dev/disk0 
  gpt remove -i 2 /dev/disk0 
  

• Re-add all partitions:

  gpt add -b 40 -i 1 -s 409600 -t C12A7328-F81F-11D2-BA4B-00A0C93EC93B /dev/disk0
  gpt add -b 391759648 -i 3 -s 1269536 -t 426F6F74-0000-11AA-AA11-00306543ECAC /dev/disk0
  gpt add -b 409640 -i 2 -s 391350008 -t 48465300-0000-11AA-AA11-00306543ECAC /dev/disk0       
  

• Verify disk and main volume and repair it if necessary:

  diskutil verifyDisk /dev/disk0
  diskutil verifyVolume /dev/disk0s2
  

• Resize the main volume:

  diskutil resizeVolume /dev/disk0s2 100% #or 250g
  

• Reboot to your main volume