How to covert MBR to GPT?

Discussion in 'OS X Mountain Lion (10.8)' started by DaYiM, Aug 4, 2013.

  1. macrumors newbie

    Apr 16, 2012
    On my secondary HDD there is two partitions,
    one with my data, & i have made the other one
    to install windows 8 on it, but when ever i want to
    install it; the installation always refuse to make it!
    Because the other partition is MBR & it have to be GPT?

    I looked around google & youtube, but the only possible way
    that i have found is to do it with windows, & i have OSX 10.8.4.

    Please Help! i really need windows, & VirtualMachine is not good enough.
  2. macrumors 65816


    Jan 18, 2008
    Northeast USA
    Just reformat that partition from within the Windows installer.
  3. macrumors 65816


    Mar 17, 2007
    That is not how it works you need to repartition the drive not format. Which Disk Utility is capable of doing although not without losing data so the OP needs to backup his data then open disk utility and select the partition option then choosing both the partition scheme wanted, drive to be partitioned and use the Options button at the bottom of the window to choose the GUID partition type before applying the changes.

    Now if you are trying to do this and use boot camp well good luck, when I set the windows up on my nephews machine it told me the only way to do it is on the primary drive with only one partition already in use for the operating system installed. You get to choose how big you want the windows partition then bootcamp does its stuff and gives you second windows partition on the drive for the installation.
  4. macrumors 6502

    Jun 22, 2010
    Perhaps this may help:

    As it says there, a backup is highly recommended before trying.

    In that guide they use /dev/disk0 which is the main hard drive. You are using a secondary hard drive. Type diskutil list ( into the Terminal to get the drive number. It is more than likely /dev/disk1.

    I hope this info is relevant to your issue. Best of luck

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