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how to dual boot high sierra and windows 10 on single HDD


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- First create 2 partitions Extended Journal when installing OS X. Make sure to jot down the size so you won't wipe out the wrong partition when you install Windows on it later.

Hint: don't make both the same size

- Use Disk Utility to prepare a Mac OS X Extended partitions (don’t ever use Fat32, Disk Utility will mess up your drive)

- After installing OS X, everything all setup. Then install Windows

- Create a FAT32 usb drive, extract Windows 10 64-bit iso there (done on a Windows system)

- Boot to Win10 usb drive, select custom install, locate the partition that is not OS X, delete it. Then select it (unallocated space) format it to NTFS, install Windows there.

- Windows will automatically boots back to Windows. Install all drivers...etc.

- Now to fix the boot option

- Go to BIOS, create boot option. Browse to /EFI/Clover/Cloverx64.efi, give it a Name. Now move the Clover boot entry to top.

- Save and reboot. Now you'll see the option to boot Windows or OS X from the Clover GUI.


To fix the time in Windows, launch regedit

navigate to 


create a DWORD (32 bit) value, name it RealTimeIsUniversal. Set the value to 1.


Boot to OSX, then reboot to Windows. You should see time is correctly sync'd up.

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Hopefully this isn't a problem to ask in this thread (as it seems related) Is there a viable way to set-up dual  boot when the SSD has an existing Windows 10 install on it? I've tried a few experiments (ahead of messing with my existing OS drive), where I shrink the Windows drive down. Then I create a simple volume (exFAT) in the space that is created. I then try to install macOS (mojave), but Disk Utility keeps declaring that MediaKit thinks there is insufficient space to format it / use it. Deleting the exFAT volume in Disk Utility seems not to help at all, and  also the action of trying to format the partition makes the Windows 10 installation unbootable.



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Is your Windows GUID formatted?

Perhaps clone Windows partition to an external drive. 

Format and install according to the steps above and then clone Windows back to the second partition.

OSX required 200MB for the EFI partition, Windows 10 defaults to 100MB, so that might be the issue there.


Check out this guide

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Ahah. I was coming here to post the same basic solution having spent some time mucking around - it does seem to be down to the rather small EFI partition from Windows. My approach used gparted to make the changes. In case useful:


In Windows, resize the Windows volume to make space for both the macOS partition and the EFI expansion.

Download tuxboot and gparted. Use tuxboot to make a bootable USB drive with the gparted software installed (see https://sourceforge.net/projects/gparted/ and the instructions at https://gparted.org/liveusb.php). Boot off the USB stick. Move the Windows partition rightwards by the few-hundred MB required to expand the EFI partition. Move the System Reserved partition rightwards as far as the tool will allow you. Now expand the EFI partition. Finally, create a new HFS+ partition in the free space after the Windows partition. Hit 'Apply' to make all these changes.

You might get an error reported by gparted, but in my case this was simply that it couldn't expand the EFI partition to the full extent, leaving a few MB unused.


In my case, I booted once into Windows, to ensure nothing was broken.

Then I went ahead with the macOS install, using the HFS+ partition as the install target.


I did have to also go into the Latitude e7480 BIOS to set an EFI entry pointing at Clover; during the install, the system would generally keep booting into Windows.


So, much the same, but I had been unclear whether the free MiniTool Partition Wizard would allow the changes needed from within the running Windows environment.



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