Editing Windows Installation

== Creating an installation disk ==

=== Mac OS ===

The flash drive should have a capacity of at least 10 Gb. <ref>[https://alexlubbock.com/bootable-windows-usb-on-mac Make a bootable Windows 10 USB drive from a Mac] -- Alex Lubbock</ref> <ref>[https://www.freecodecamp.org/news/how-make-a-windows-10-usb-using-your-mac-build-a-bootable-iso-from-your-macs-terminal/ How to Make a Windows 10 USB Using Your Mac - Build a Bootable ISO From Your Mac's Terminal] -- freeCodeCamp</ref>

==== Identify the drive where the USB flash drive is mounted ====

Insert the flash drive on a Mac.

Open a terminal window. 

<pre>
$ diskutil list
</pre>

This should display all the disks currently mounted on the system along with the USB flash drive. Take note of the `IDENTIFIER` value, e.g. `/dev/disk2`.

==== Format the USB flash drive ====

<pre>
$ diskutil eraseDisk MS-DOS "WIN10INST" MBR /dev/disk2
</pre>

* `MS-DOS` is the filesystem
* `"WIN10INST"` will be the name of the drive. This can be any arbitrary name.
* `GPT` is the partition type. "GPT" is necessary for PCS that boot in UEFI mode. 
* `/dev/disk2` is the identifier of the USB drive. This identifier could be a different value depending on the Mac.

<p class="alert alert-warning">One guide for creating the installation flash drive recommended using the `GPT` option in place of `MBR` when formatting the drive. Using the `GPT` option caused many errors and ultimately did not create a drive that could be used to successfully install Windows. It would boot, and the Windows installation would start, but the installation would fail at various points with a variety of error messages.</p>

After using the `GPT` option there would be two partition options for booting from the disk. With the `MBR` option, there is only one partition option for booting from the disk.

'''MBR''' stands for Master Boot Record and '''GPT''' stands for GUID Partition Table. 

==== Mount the Windows ISO ====

<pre>
$ hdiutil mount ~/Downloads/software/Win10_20H2_v2_English_x64.iso
</pre>

The path to the Windows ISO file can be different, of course. It would be wherever the file was downloaded.

==== Copy the Windows 10 ISO to the USB flash drive ====

Mac OS doesn't read NTFS filesystem natively. This is why the USB drive is formatted using MS-DOS. However some files (e.g. `install.vim`) are too large to copy to MS-DOS. They need to be split and then copied over.

First copy all the files except the ones that are too large:

<pre>
$ rsync -vha --exclude=sources/install.wim /Volumes/CCCOMA_X64FRE_EN-US_DV9/* /Volumes/WIN10INST
</pre>

Again, the names of the volumes may be slightly different.

Now copy files that are over 4Gb. This requires `wimlib` which can be installed with homebrew.

<pre>
$ brew install wimlib
</pre>

Split the file(s) into 3800Mb parts in order to accommodate the MS-DOS limits.

<pre>
wimlib-imagex split /Volumes/CCCOMA_X64FRE_EN-US_DV9/sources/install.wim /Volumes/WIN10/sources/install.swm 3800
</pre>

Again, the paths to the source and destination directories may be slightly different.

==== Eject the USB drive ====

The installation drive is ready to be used. Power off the PC. Insert the USB drive in the PC. Load the BIOS on the PC and select the USB drive as the primary boot drive.

== Troubleshooting ==

=== Windows installer complains that it can't install from or on a particular drive ===

'''Possible cause'''

The Windows installer can't boot from EFI/UEFI drives.

'''Solution'''

Look at the boot order in the BIOS. The primary boot drive should not start with UEFI or EFI. If the USB drive starts with UEFI, the installation files must be copied to a drive (SATA) that does not start with UEFI and the installer must be booted off that drive.

=== Can't create a new partition or locate an existing one ===

'''Error'''

Error: "We couldn't create a new partition or locate an existing one." on the '''Where do you want to install Windows?''' prompt.

'''Cause'''

The installer is having difficulty installing from the flash drive.

'''Solution'''

Create a partition on the hard drive and copy the Windows install files there. <ref>[https://answers.microsoft.com/en-us/windows/forum/windows_10-windows_install/we-couldnt-create-a-new-partition-or-locate-an/acdb1dae-01d9-44f7-846c-433e5addcfc2?auth=1 We couldn't create a new partition or locate an existing one.] -- answers.microsoft.com</ref>

* Plug the flash drive with the installer on it into an USB port. 
* Boot from the flash drive.
* At the '''Where do you want to install Windows?''' screen displaying the error message press <kbd>Shift</kbd> + <kbd>F10</kbd> to get a command prompt.

<pre>
> diskpart
> list disk
> select disk 0
> clean
> create partition primary size=5000
> format fs=ntfs quick
> assign
> active
> list volume
> exit
> cd c: 
> xcopy e: c:/e/h/k
> exit
</pre>

* `select disk 0` selects the hard drive onto which the installation files will be copied.
* `create partition` makes a partition on the hard drive where the installation files can be copied.
* `assign` assigns a drive letter to the new partition.
* `xcopy` copies the installation file from the USB drive to the hard drive.
* The last `exit` closes the command prompt window.

* After closing the command prompt, remove the USB flash drive and click the '''X''' button at the top right of the Windows installation window to close the current installation and reboot the computer.
** Without a mouse, click <kbd>Esc</kbd>, the confirm to quit the installation. If this leads back to the first window of the Windows installation, click <kbd>Esc</kbd> again, and again confirm that the installation will be canceled.
* The computer should now boot from the hard drive and the installation will use the files from the new partition.

== Notes ==

=== References ===
<references />
[[category:Windows]]