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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/

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    Did you try Internet Recovery? – user255044 Mar 8 '18 at 7:29
  • Yes, I believe so. I get the apple logo, and the prohibitory symbol appears.🚫 – theboss1412 Mar 8 '18 at 20:24
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    Wow, you picked instructions for installing Vista! You do need help. Apple make changes to the Mac designs with each model released. To help you properly, you would need to add the following information to your question: 1) Model/year of your Mac? 2) Version of macOS (OS X) you wish to install? 3) Any OS X installation DVDs you may have? 4) Does you model have a working DVD drive? 5) does the Windows 7 include any Service Packs? 6) Was Windows 7 a 32 bit or 64 bit version? 7) do you have any other working Mac to download file? If so, what model/year and version of macOS (OS X)? – David Anderson Mar 8 '18 at 22:57
  • @DavidAnderson 1. 2012 MC309LL 2. EL Capitan 3. No installation disks for mac at the moment 4. Dvd drive is working 5. No service packs 6. Windows 7 64 bit I have no other mac arounds, unfortunately – theboss1412 Mar 9 '18 at 11:24
  • Are you sure you iMac is a 2012 model? This web site shows your iMac is a 2011 model. Are you sure your Windows 7 does not contain any service packs. I ask because according to this Apple website, Windows 7 has to have Service Pack 1 (SP1) in order to correctly install on any Mac. By the way, if the identifier is correct, then I as using the exact same model iMac. I can tell you for certain, that when correctly installed, Windows 7 and 10 both work great on this model/year iMac. – David Anderson Mar 9 '18 at 11:44
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Reinstall macOS (OS X)

  1. Boot to Internet Recovery. See instructions below. You may need to reset your NVRAM. If so, see instructions below.
  2. Use the Disk Utility app to erase the internal drive. Choose for Mac OS Extended (Journaled) for the format.
  3. Install macOS (OS X).
  4. Boot to macOS (OS X).
  5. 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.
  6. If the operation system is 10.6.8, then install this Mac App Store Update for OS X Snow Leopard
  7. Upgrade to 10.11.6.

Start up from macOS (OS X) Recovery over the Internet

  1. Turn on or restart your Mac, then immediately hold down the option++R key combination.
  2. Release the keys when you see the Apple logo or a spinning globe.
  3. When you see the macOS (OS X) Utilities window, you have finished booting.

Reset your computer’s NVRAM or PRAM

  1. Shutdown the Mac.
  2. Locate the following keys on the keyboard: option, , P, and R. You will need to press and hold these keys simultaneously in step 4.
  3. Turn on your Mac.
  4. Immediately press and hold the option++P+R key combination, before the black screen with the Apple logo appears.
  5. Continue pressing the keys until your Mac restarts, about 15 seconds.
  6. Release the keys.

Appendix

How to reset NVRAM on your Mac

How to reinstall macOS

About macOS Recovery

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