Let's face it, letting Windows Setup absolutely sucks at creating Partitions. Let's take for example this Unallocated Space on a Drive and see what happens when Windows 10 1903 is installed with BIOS (MBR) and UEFI (GPT)
BIOS MBR Windows Setup Defaults
On the outside, this doesn't look too bad, just two partitions. WinRE is in System Reserved
But by Microsoft's own guidance, that's not how it should look ...
And Microsoft even provides you with the code to do it (PowerShell????)
rem == CreatePartitions-BIOS.txt ==
rem == These commands are used with DiskPart to
rem create three partitions
rem for a BIOS/MBR-based computer.
rem Adjust the partition sizes to fill the drive
rem as necessary. ==
select disk 0
clean
rem == 1. System partition ======================
create partition primary size=100
format quick fs=ntfs label="System"
assign letter="S"
active
rem == 2. Windows partition =====================
rem == a. Create the Windows partition =======
create partition primary
rem == b. Create space for the recovery tools
rem ** Update this size to match the size of
rem the recovery tools (winre.wim)
rem plus some free space.
shrink minimum=500
rem == c. Prepare the Windows partition ======
format quick fs=ntfs label="Windows"
assign letter="W"
rem == 3. Recovery tools partition ==============
create partition primary
format quick fs=ntfs label="Recovery"
assign letter="R"
set id=27
list volume
exit
But again, Windows Setup doesn't play by the rules
rem == CreatePartitions-UEFI.txt ==
rem == These commands are used with DiskPart to
rem create four partitions
rem for a UEFI/GPT-based PC.
rem Adjust the partition sizes to fill the drive
rem as necessary. ==
select disk 0
clean
convert gpt
rem == 1. System partition =========================
create partition efi size=100
rem ** NOTE: For Advanced Format 4Kn drives,
rem change this value to size = 260 **
format quick fs=fat32 label="System"
assign letter="S"
rem == 2. Microsoft Reserved (MSR) partition =======
create partition msr size=16
rem == 3. Windows partition ========================
rem == a. Create the Windows partition ==========
create partition primary
rem == b. Create space for the recovery tools ===
rem ** Update this size to match the size of
rem the recovery tools (winre.wim)
rem plus some free space.
shrink minimum=500
rem == c. Prepare the Windows partition =========
format quick fs=ntfs label="Windows"
assign letter="W"
rem === 4. Recovery tools partition ================
create partition primary
format quick fs=ntfs label="Recovery tools"
assign letter="R"
set id="de94bba4-06d1-4d40-a16a-bfd50179d6ac"
gpt attributes=0x8000000000000001
list volume
exit
