Ursprünglicher Beitrag von: S W ,
1) In the Apple menu, choose Restart or power on your Mac. 2) As the computer restarts, hold down the Command (⌘) – Option (⌥) – R combination immediately upon hearing the startup chime. Hold the keys until the animated globe appears on the screen. “Starting Internet Recovery,” the message reads. ”This may take a while.” 3) Select your method of Internet connection and wait wil Internet Recover downloads. 4) Use Disk Utility to format and partition the drive, then reinstall OS X fresh.