Wondering if anyone has done this before? My 2009 mac mini has windows 7 on it presently and I know that I formatted the thing with windows entirely to make this happen.

Now when I try and boot off my bootable USB installer for Yosemite to get OSX installed back onto it, holding the option key down doesn't bring up drives it just continues to boot to windows.

Any help appreciated in advance!

Is it possibly because the format of the drive is not GUID-partition but FAT?


What you can do is called resetting the NVRAM (non-volatile random access memory).

Resetting NVRAM

  1. Shut down your Mac.
  2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
  3. Turn on your Mac.
  4. Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
  5. Hold these keys until the computer restarts and you hear the startup sound for a second time.
  6. Release the keys.

After you do this, hit the startup key, then hold alt when you hear the startup chime. You should be able to select the USB as a bootable drive.

Source: https://support.apple.com/en-us/ht204063

  • Though I believe your computer actually might have PRAM (not quite sure about the dates), the key combination and the functions are exactly the same. Parameter RAM is just an older form of NVRAM, essentially. – Addison Crump Jul 14 '15 at 5:52

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