I have a mac book air, which was formatted a long time ago, and only has windows running on it.

I would like to run Mac OS again instead of windows. Or if that isnt possible, have both OS's.

How can I get Mac OS installed on this machine again?

  • Though n1000's answer will work - it might just be worth checking by holding Opt at the boot chimes, just to see if any remnant of OS X is still on there. If so you could build from that rather than wipe & start over.
    – Tetsujin
    Feb 20, 2015 at 7:28

1 Answer 1


The easiest way is probably to use OS X internet recovery:

  1. Press cmd+alt+R at startup
  2. Open the disk utility from the opening menu
  3. Reformat the disk to HFS+ Journaled
  4. Close disk utility and go to install OS X

This procedure will delete all your data and Windows completely.


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