SaxBoy126
Level 1 (0 points)

Q: Accidentally Formatted Mac OS Partition Under Windows

Hi guys,

 

I recently bought a Macbook Air 13", I tried installing windows on it and I formatted the Mac OS drive to NTFS under windows....now my mac only has windows on it..

 

Just wondering How do I install Mac OS back?

 

Thanks so much!!!!

MacBook Air

Posted on Nov 8, 2012 11:12 PM

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SaxBoy126

Q: Accidentally Formatted Mac OS Partition Under Windows

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  • by mende1,

    mende1 mende1 Nov 8, 2012 11:16 PM in response to SaxBoy126
    Level 10 (93,314 points)
    Desktops
    Nov 8, 2012 11:16 PM in response to SaxBoy126

    Welcome to the Apple Support Communities

     

    Press Command and R keys on boot and reinstall Mountain Lion. If Mountain Lion tells that the disk isn't formatted on Mac OS Extended, close the installer, open Disk Utility and erase the drive

  • by thomas_r.,

    thomas_r. thomas_r. Nov 9, 2012 4:26 AM in response to SaxBoy126
    Level 7 (30,889 points)
    Mac OS X
    Nov 9, 2012 4:26 AM in response to SaxBoy126

    You will need to reformat the drive as "Mac OS Extended (Journaled)" using Disk Utility. You may also need to repartition it, depending on whether what you did with Windows changed the partition map scheme.

     

    Screen Shot 2012-11-09 at 7.17.34 AM.png

    If it's not GUID, select the partition tab, click the Options button and change it to GUID. Then set the Partition Layout to one partition (or leave it set to "Current" if there's already only one), set that partition to be Mac OS Extended (Journaled), and click the Apply button.

     

    As mende1 said, you hold command-R at startup to enter recovery mode, which allows you to access Disk Utility or reinstall the system. Note that an internet connection will be required, and you will need to download about 4 GB of data (or more if Windows destroyed your hidden recovery partition and the machine has to boot over the internet from a system on Apple's servers).

  • by r7_human8y,

    r7_human8y r7_human8y Feb 12, 2015 6:16 PM in response to thomas_r.
    Level 1 (0 points)
    Feb 12, 2015 6:16 PM in response to thomas_r.

    Hi Guys,

     

    I have the same problem with the above.

     

    I installed windows using bootcamp last night on my iMac, the because I was on the phone, I accidentally reformatted the mac partition (Yosemite OS), so currently I only have the windows when I tried to open the iMac.

     

    I tried the shortcut keys to do internet recovery, but my iMac wont simply allow as it is late 2009 model.

     

    Can you help me on how can I re-install again the Yosemite os and use the remaining disk capacity?

     

    Looking forward to your response.