- Be sure you have a full backup as this will destroy all data on the drive.
- Reboot and when you hear the bong press and hold Option.
- Click the drop down menu Choose Network > select your wifi network and connect to it.
- Press Command+Option+R. OS X Utilities will download and launch.
- Choose Disk Utility
- On the left select your hard drive > On the right side at the top choose Erase > Click Erase on the bottom right.
- Close the Disk utility.
- Choose Reinstall OS X
