A UEFI boot USB device must be FAT32. Or at least contain a FAT32 boot partition. Is that correct?
No! While it is true that some BIOS don't support booting from NTFS formatted UFDs (USB Flash Drives), this is NOT technically due to any lack of support by the UEFI specification. The maker of RUFUS has a detailed discussion about this very topic on their web site.
I use a method that I learned on TenForums several years ago that works for booting Windows images or WinRe / WinPE based media like Macrium Reflect recovery disk, etc. on ANY system. It doesn't matter if your system is BIOS or UEFI based.
Try this procedure. Note: The instructions are for making a Windows boot disk, but this applies also to other WinRE / WinPE based media.
Bootable Flash Drive Using Only Native MS Tools
1) Run diskpart.
2) From the diskpart> prompt, run this command:
list disk
3) From the size of the disks, try to determine which disk ID is your thumb drive. If that is not enough information, run these commands to get more detail on the disk. In this example, I want more info on disk 4:
select disk 4
detail disk
Here is some sample output:
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
Disk 0 Online 476 GB 0 B *
Disk 1 Online 3726 GB 0 B *
Disk 2 Online 465 GB 1024 KB *
Disk 3 Online 7452 GB 0 B *
Disk 4 Online 238 GB 0 B
DISKPART> select disk 4
Disk 4 is now the selected disk.
DISKPART> detail disk
SanDisk Extreme Pro USB Device
Disk ID: DC727760
Type : USB
Status : Online
Path : 0
Target : 0
LUN ID : 0
Location Path : UNAVAILABLE
Current Read-only State : No
Read-only : No
Boot Disk : No
Pagefile Disk : No
Hibernation File Disk : No
Crashdump Disk : No
Clustered Disk : No
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 7 Z My Software NTFS Removable 238 GB Healthy
C:\MountPoints\My Software\
4) When you determine the correct disk, run these commands. I am assuming disk 5 in the following example:
select disk 5
clean
convert mbr
create partition primary size=2000
active
format fs=fat32 quick
assign
create partition primary
format fs=ntfs quick
assign
exit
NOTE: The assign commands will assign the next available drive letter. If you want to assign specific drives letters, for example E:, use the command
assign letter=E
.
5) We will now copy files from the source to the two partitions on the thumb drive. To be clear, all the files and folders that you are being asked to copy come from your source folder such as a folder on your hard disk that contains all the Windows files, or from a mounted Windows ISO image.
Start by checking to see if your original source has a file called ei.cfg in \sources folder. If that file is already present, skip to step 6. Also, if you are working with something other than a Windows Setup image, please skip to step 6.
Create a text file called
ei.cfg
. We will use that below. Place the following 2 lines into that file:
[Channel]
Retail
Notes about ei.cfg: Let's say that you have a computer that shipped with Windows 10 Home, but you upgraded to Pro. You may find that when you try to perform a clean install, Windows simply starts installing Home and doesn't even show you the menu from which you can select other editions. By placing this file in the sources folder, we prevent that from happening. This happens because Windows setup reads a signature in the BIOS that tells setup which edition of Windows the system was shipped with.
Note that when doing an unattended install, this file is not needed because the autounattend.xml specifies the edition of Windows to install, but you can leave the ei.cfg in place as it won't hurt anything.
6) Follow these steps to copy files to your thumb drive:
• Copy all files and folders
EXCEPT the
\sources
folder to the FAT32 partition (the first, smaller partition).
• If you are planning to use an autounattend.xml answer file, place it in the root of either partition.
• Create a folder called
sources
on the FAT32 partition.
• Copy the file
\sources\boot.wim
to the FAT32 partition
\sources
folder.
• Create a folder called
sources
on the NTFS partition (the second, larger partition).
• Copy all files and folders from the
\sources
folder
EXCEPT boot.wim
to the
\sources
folder on the NTFS partition.
• If you created an
ei.cfg
file, copy it to the
\sources
folder of the NTFS partition.
At this point, you should have a bootable thumb drive.
NOTE: When booting you may be presented with an option to boot either the FAT32 or the NTFS partition. Choose the FAT32 partition. If it is not clear which one the FAT32 partition is, simply try either. If it doesn't work, reboot and try the other. Usually the FAT32 partition is listed first.