Installed Windows on Mac, now want to go back to OS X
I tried to revert back to OS X, but I can't boot into recovery, or USB. It shows the prohibited symbol (a circle with a line through).
I thought it was a good idea to install Windows on a Mac, but it turns out it's a terrible idea (driver issues, slow downs, overheating).
What should I do?
I think my hard drive partitions are messed up.
I used this guide to install windows 7 http://derekhat.com/install-vista-on-a-macbook-without-bootcamp/
Reinstall macOS (OS X)
- Boot to Internet Recovery. See instructions below. You may need to reset your NVRAM. If so, see instructions below.
- Use the Disk Utility app to erase the internal drive. Choose for
Mac OS Extended (Journaled)
for the format. - Install macOS (OS X).
- Boot to macOS (OS X).
- If the operating system is Snow Leopard and the version is not 10.6.8, then download and install this Mac OS X 10.6.8 Update Combo v1.1.
- If the operation system is 10.6.8, then install this Mac App Store Update for OS X Snow Leopard
- Upgrade to 10.11.6.
Start up from macOS (OS X) Recovery over the Internet
- Turn on or restart your Mac, then immediately hold down the option+⌘+R key combination.
- Release the keys when you see the Apple logo or a spinning globe.
- When you see the macOS (OS X) Utilities window, you have finished booting.
Reset your computer’s NVRAM or PRAM
- Shutdown the Mac.
- Locate the following keys on the keyboard: option, ⌘, P, and R. You will need to press and hold these keys simultaneously in step 4.
- Turn on your Mac.
- Immediately press and hold the option+⌘+P+R key combination, before the black screen with the Apple logo appears.
- Continue pressing the keys until your Mac restarts, about 15 seconds.
- Release the keys.
Appendix
How to reset NVRAM on your Mac
How to reinstall macOS
About macOS Recovery