Okay thanks for staying with me.
If you’ve followed along so far, then your Mac is booted to a UEFI-native installer. You’re looking at the Windows Install splash screen that says “Install Now”
Don’t click it. Shift+F10 will open a terminal window, which makes you some kind of god. Feel it. Enjoy it. Run diskpart
Once it’s loaded, you need to use your brain.
Will show you the physical disks attached to the system. Using your intelligence, choose which one you’re using for Windows installation. These will be named “disk 0” “disk 1” “disk 2” et cetera, et cetera…
What is it with everyone and Peter Cetera? Jeez. Look, whatever.
Once you’ve identified which is the main internal boot disk by its number… Assuming that it’s disk 0…
select disk 0
create partition efi size=300
create partition primary
This list of commands will select the primary internal fixed disk (HDD or SSD) erase everything – all partitions and all data within them – It transforms the disk into a GPT format disk, required for UEFI. It then builds an EFI partition, which is the modern version of the MBR and formats it. Finally it creates a primary partition that fills the disk.
format fs=ntfs quick label=Windows
This formats the primary partition for Windows in the NTFS format. The Fall Creators Update can no longer create a ReFS drive for Windows unless you have the Windows 10 Pro for Workstations of Windows 10 Enterprise SKUs.
Once the format is complete, just type “exit” and diskpart will exit.
Close the terminal window and continue Windows setup as normal.
If you’ve installed Windows 10 using an MS Account, then you have no need to add a product key. Just install and add that MS account after install. Once it’s done, it will tie that install to your MS account.
Smaller details and errors I have not encountered are not fair, but I’m very willing to help. Please post and I’ll do my best to help. I really really hope that others will also join in helping with installation errors.