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I recently had a working Boot Camp partition with Windows 7 operational. I made the mistake of creating a 3rd partition to install a version of macOS do to program requirements, attempting to keep the older OS X El Capitan partition for depreciated programs. I then realized Boot Camp only allows for up to 4 partitions and proceeded to remove the new fourth partition and restore the previous 4 partition configuration with a Time Machine backup. Unfortunately, after the system restore, I am left unable to boot to Windows 7 with the option key on startup.

I'm very much hoping there is a way to restore functionality to the Boot Camp partition. It is still viewable in the device list but in Disc Utility it is not visible. In Recovery boot, the partition is listed as it would normally. I will post some pertinent info below:

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Windows 7 uses the MBR partition table. Currently this table only has one entry. You will need to edit the first entry and add the 3 missing entries. This can be accomplished by using the gdisk command. The installer for this command can be download from this GPT fdisk SourceForge website.

Note: To use gdisk, SIP needs to be disabled.

The command to enter in a Terminal application window is given below.

sudo gdisk /dev/disk0

The gdisk command is interactive. Below are the entries to be made.

Entry Type Comment
r command Goto recovery and transformation menu
h command Make hybrid MBR
2 3 4 parameter GPT partition numbers to copy from
y parameter Place EFI GPT (0xEE) partition first in MBR
af parameter MBR hex code for 2nd partition
n parameter Do not set the bootable flag for 2nd partition
ab parameter MBR hex code for 3rd partition
n parameter Do not set the bootable flag for 3rd partition
07 parameter MBR hex code for 4th partition
y parameter Set the bootable flag for 4th partition
w command Write MBR partiton table to disk and exit
y parameter Confirm write and exit

Note: Making changes to the MBR partition table may result in have to rebuilt the Windows 7 Boot Configuration Data (BCD) file.


BTW, you can have more than four partitions. In other words, you did not have to "remove the new fourth partition and restore the previous 4 partition configuration". For example, if you added a new APFS partition as the fourth partition, then you could have entered 2 3 5 in gdisk instead of the 2 3 4 entry given in the above table.

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