After using the Boot Camp Assistant to install Windows, is it possible remove macOS and add the free space to Windows?

Removing macOS and Adding the Free Space to Windows

The steps are given below.

1. Make Windows the default operating system to boot. This can be done from the System Preferences application or from the Mac Startup Manager.

2. Boot to Windows and download the free version of the MiniTool Partition Wizard. The file I downloaded was pw-free-online.exe.

3. Open a Administrator Command Prompt window and use the diskpart command to replace the APFS partition containing macOS with a 16 MB Micrsoft Reserved (MSR) partition.

   diskpart
   list disk
   select disk 0
   list partition
   select partition 2
   delete partition
   create partition msr size=16
   list partition
   exit
   exit
   

4. Install the MiniTool Partition Wizard. Be careful to just install the free version of the MiniTool Partition Wizard.

5. Add the free space to Windows. Open the MiniTool Partition Wizard. Below is an example where there is 99.9 GB of free space before the Windows partition.

   

   Add the free space to the Windows partition by resizing the partition. This should appear as a pending operation, as shown below.

   

   Next, select the “Apply” button is apply this pending operation. When prompted, select the “Restart Now” button. The resize operation will occur during the restart.

Explanation of What the Resize Operation Did

I installed Puran Defrag for the purposes of showing the location of the drive C: clusters before and after the resizing. This of course is something you do not have to do. Since I started with a clean install of Windows 10, all the clusters occur at the beginning of drive C:, as shown below.

After the resize from approximately 100 GB to 200 GB, the clusters now appear in the center drive C:, as shown below.

What the images illustrate is that for the most part, the files did not move with respect to their Logical Block Address (LBA) on the physical drive. The free space was actually added to the beginning of the drive C: volume without relocating a majority of the files. This makes this resize operation occur must faster than other methods that move files or entire partitions.

Example of Commands Entered in the Administrator Command Prompt Window

Microsoft Windows [Version 10.0.19045.2965]
(c) Microsoft Corporation. All rights reserved.

C:\Windows\system32>diskpart

Microsoft DiskPart version 10.0.19041.964

Copyright (C) Microsoft Corporation.
On computer: DESKTOP-28FFUEF

DISKPART> list disk

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
  Disk 0    Online          200 GB      0 B        *

DISKPART> select disk 0

Disk 0 is now the selected disk.

DISKPART> list partition

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    System             200 MB    20 KB
  Partition 2    Unknown             99 GB   200 MB
  Partition 3    Primary             99 GB   100 GB

DISKPART> select partition 2

Partition 2 is now the selected partition.

DISKPART> delete partition

DiskPart successfully deleted the selected partition.

DISKPART> create partition msr size=16

DiskPart succeeded in creating the specified partition.

DISKPART> list partition

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    System             200 MB    20 KB
* Partition 2    Reserved            16 MB   201 MB
  Partition 3    Primary             99 GB   100 GB

DISKPART> exit

Leaving DiskPart...

C:\Windows\system32>exit