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Failure to Install Windows OS from Mac Boot Camp Assistant

“Windows could not prepare the computer to boot into the next phase of installation. To install Windows, restart the installation.”


  • Unable to install windows OS from boot camp assistant
  • Restarting the installation process results in the error message loop above


  1. Acknowledge the error message and click “OK”
  2. Windows Setup will attempt to restart the installation process, click and exit out of the windows setup by clicking the red “X”
  3. A message should appear:

“To install Windows, you must run Windows installation. If you cancel the installation, your computer might restart”

4. Locate (do not press yet) the “Option”, “Command”, “R”, and “P” keys on the mac device.

4. Confirm the windows installation cancellation by clicking “Yes” and the computer will automatically restart

5. When you hear the apple boot up chime sound. Quickly, press and hold down the “Option”, “Command”, “R”, and “P” keys on the mac device. This will reset your NVRAM and PRAM, freeing up necessary space in your RAM for the installation to continue.

6. The computer will automatically restart, resetting your NVRAM and PRAM in the process. Once you hear the second apple boot up chime sound, you may stop holding down the Option, Command, R, and P keys

7. Mac OS will boot up normally.

8. Open Boot Camp Assistant application.

9. Uncheck the first two options (create usb and download boot camp drivers). Only check the last option, which is to remove the Windows partition.

10. Restore Disk to a Single Partition Volume. Confirm by clicking “Restore”

11. Re-open the Boot Camp Assistant application.

12. Restart the installation of Windows. Assuming you already created a bootable USB and have already downloaded the boot camp drivers, uncheck these options and only check the last option to install windows.

13. Re-create the size for Windows Partition and click “Install“.

14. Computer will restart and the windows setup will appear again.

15. Follow instructions on the screen until you get to the partition menu

16. Format the newly created windows partition by clicking on the partition size you created (It will be a little smaller than you specified). Click “Format” and then “Next” to finish.

If step 16 fails and you receive this message, complete steps 17-20. Else proceed to step 21.

Your disk could not be partitioned. An error occurred while partitioning the disk.”

17. Launch “Disk Utility” (Applications > Utilities > Disk Utility)

18. In the left-hand panel, click on your hard drive

19. Click “Verify Disk”

20. If there are any errors, try clicking “Repair Disk”.

If repair worked successfully, try re-running Boot Camp Assistant

21. Setup will complete without error this time and will automatically restart into your Windows OS when finished.

22. Whenever you need to swap back to the Mac OS, simply restart the computer and hold down the “Option” key and then select the desired OS.

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