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I have a mid-2011 iMac and I installed Windows 7 in Bootcamp by the help of this link .

$ diskutil list

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            1.5 TB     disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data BOOTCAMP                499.3 GB   disk0s4

Then, I need to a new partition for my media data. I tried to add an ExFAT partition by splitting disk0s2 via DiskUtility and resulted into following...

$ diskutil list

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            496.8 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s6
   4:       Microsoft Basic Data data                    1.0 TB     disk0s7
   5:       Microsoft Basic Data BOOTCAMP                499.3 GB   disk0s4

$ sudo fdisk /dev/disk0

Disk: /dev/disk0    geometry: 243201/255/63 [3907029168 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: EE 1023 254  63 - 1023 254  63 [         1 -     409639] <Unknown ID>
 2: AF 1023 254  63 - 1023 254  63 [    409640 -  970300304] HFS+        
 3: AB 1023 254  63 - 1023 254  63 [ 970709944 -    1269536] Darwin Boot 
 4: 07 1023 254  63 - 1023 254  63 [ 971979480 - 1959233472] HPFS/QNX/AUX

$ sudo gpt -r show /dev/disk0

gpt show: /dev/disk0: Suspicious MBR at sector 0
       start        size  index  contents
           0           1         MBR
           1           1         Pri GPT header
           2          32         Pri GPT table
          34           6         
          40      409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
      409640   970300304      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
   970709944     1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
   971979480  1959233472      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
  2931212952      262144         
  2931475096   975291888      5  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
  3906766984      262151         
  3907029135          32         Sec GPT table
  3907029167           1         Sec GPT header

After adding the ExFAT partition, BootCamp not working, I could not boot iMac with Widows 7. (cannot find bootable disk...)

I believe the point of mine is that the index number of BOOTCAMP partition is #5 after this partitioning. It was #4 before then. This means I cannot make the BOOTCAMP partition 'active' with 'fdisk' or 'diskpart'. Am I right?

Finally I removed the ExFAT partition and set the BOOTCAMP partition(#4) 'active' manually.

Is there any way to add an ExFAT partition on my iMac without reinstalling Windows 7? Or any other points to be considered in my case?

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You do not have to assign partitions 2, 3, and 4 of the GPT to the same partitions 2, 3 and 4 of the MBR partition table. In other words, you could have skipped partition 3 of the GPT to produce the result shown below.

Disk: /dev/disk0    geometry: 243201/255/63 [3907029168 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: EE 1023 254  63 - 1023 254  63 [         1 -     409639] <Unknown ID>
 2: AF 1023 254  63 - 1023 254  63 [    409640 -  970300304] HFS+        
 3: 07 1023 254  63 - 1023 254  63 [ 971979480 - 1959233472] HPFS/QNX/AUX 
*4: 07 1023 254  63 - 1023 254  63 [2931475096 - 975291888 ] HPFS/QNX/AUX

While modifying the MBR partition table with the fdisk command is possible, the third party gdisk command is much easier to use. Windows 7 may see the change in partition 3 as an attempt to move Windows to a different machine. If this happens, Windows will not boot. The solution would be to use the bootrec /RebuildBcd command to rebuild the BCD file. The instructions are provided at the Microsoft website: Use Bootrec.exe in the Windows RE to troubleshoot startup issues. You would not have to reinstall Windows 7.

Note: The macOS operating system may occasionally view this partitioning scheme as an error and change the MBR partition table back to either a full protected MBR or replace partitions 3 and 4 with partitions 3 and 4 of the GPT. If this happens, you will need to manually fix the MBR partition table. You would not have to rebuild the BCD file.

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  • Thank you for your great idea, it is working like a magic for me. Although bootrec /RebuldBcd produced ..found no element.., everything is very good in my old iMac. – Hoon Lee Apr 27 '18 at 12:01

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