I want to remove Windows from Mac and the I know the simple way is through the Boot Camp Assistant. But that doesn't work for me as follows:

the remove button is greyed out

However, when I try to merge the partition of windows through disk utility, all buttons are inactive, and I cannot press either '-' or 'option' button, like follows:

cannot merge the partition

Then, I try to reinstall a new Mac osX from the internet by pressing and holding the [command]+[alt]+[R] when starting the computer, and it doesn't work either. I am informed that the system cannot be installed in either the BOOTCAMP partition or Untitled partition since they are not GUID partition table format.

I am a newer to Mac and I just want to delete the Windows partition and add the space back to my osX partition. I wonder what should I do next?

Thanks for help!

3 Answers 3


First of all, try both repair disk (if grayed, then verify), and repair disk permissions. If you are still unable, boot to single-user mode (Command +S on boot) and type in the following.

/sbin/fsck -fy

Press enter, then type reboot.

If it still does not work, then do the following, but be sure to backup:

Hold Command +R on boot to start Recovery mode, select disk utility and do it from there. If it is grayed out, select the partition scheme to 1 (or 2 if you need Untitled)


There have been reports that setting the partition scheme to 1 or 2 can erase all your data. Be sure to backup before attempting to do this.

  • If you go so far as to select the entire device, then take this advice to set it to 1 partition and apply it, you will lose the entire drive.
    – user193259
    Commented Jul 23, 2016 at 13:53
  • @RayJunior I will add that, if there's a risk. It always worked for me.
    – John K
    Commented Jul 30, 2016 at 15:05

Okay, so when I had a similar problem, I used Terminal, these two guides, and this command line to get it done.

diskutil mergePartitions JHFS+ NewName {first disk identifier in range} {last disk identifier in range}

I used diskutil list to make sure I knew which drives I was merging, because you can't use the Disk Utility names (Macintosh HD, BOOTCAMP), you need the disk identifier (which looks like disk0, disk0s1, disk0s2, etc). I'm going to guess your HD would be disk0s2 and the BC is disk0s3, if that were true the next thing you'd put into Terminal is:

diskutil mergePartitions JHFS+ NewName disk0s2 disk0s3

The JHFS+ will reformat the Windows drive when it merges and NewName should be replaced with whatever you wanna name your HD.

Mind you, doing the above should leave you with 2 partitions: NewName and Untitled. If you wanted to merge all three partitions then you would use HD and Untitled in your command line.

  • Answers on Ask Different need to be more than just a link. It's okay to include a link, but please summarize or excerpt it in the answer. The idea is to make the answer stand alone.
    – nohillside
    Commented Jul 23, 2016 at 18:54

Be careful diskutil mergePartitions is very powerful -- if you have segment A and C and merge them it gets rid of B (merges that too) -- and other very funky repercussions. So be careful.

It ultimately helped me get rid of the xfat partition but it was tricky.

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