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03 Oct 2025 - by 'Maurits van der Schee'
When you buy a Windows PC it comes bundled with a lot of software that you do NOT want. To remove this unwanted software it is recommended to do a "clean install" of Windows 11. When copying the install disk (Windows 11 ISO) to a bootable USB drive you may run into the problem that you can't copy the "install.wim" file. This post has a solution to that problem.
When I get a new PC (such as my new GMKTec M6 Ultra mini PC) I like to do a clean Windows 11 install. This removes the manufacturer's bundled software. Since this mini PC supports secure UEFI boot it should be as easy as initializing a USB drive with a "GPT partition table" and creating a FAT32 partition with the contents of the installation ISO (you can just copy the files). In UEFI boot there is no need for changes to the "Master Boot Record" or for a "boot flag" on the partition.
Note that a clean install also removes the bundled drivers from your system. This may prove cumbersome when the latest version of Windows does not support your WiFi or Ethernet port (you may need to transfer them using a USB stick).
In order to be able to write an ISO to a FAT32 partition there may be no file bigger than 4 gigabytes. This is a problem, as in the latest Windows 11 the "sources/install.wim" file is 6.3 GiB in size. We can work around this problem by splitting this file into multiple 1 GiB files (this split format is supported by the Windows 11 installer). The splitting options are described on wimlib.net. We are going to use a 1 GiB split size just to be sure.
You can download the official Windows 11 ISO image from Microsoft by visiting:
https://www.microsoft.com/nl-nl/software-download/windows11
You get a link that is valid for 24 hours to download the ISO that is 7.1 GiB in size
In Ubuntu you can just right click any ISO image and "Open with Disk Image Mounter". You can now copy all contents to a new folder on your hard disk. Now find the "sources" folder in the copied disk, enter it and right-click and choose "Open Terminal Here". In this terminal you need to run one command:
Subscribewimsplit install.wim install.swm 1024 --check
If you have not got this tool yet you may have to install WimLib tools first:
sudo apt install wimtools
On my machine this was the output (I ran it with "time" so that you can see how long it took):
$ time wimsplit install.wim install.swm 1024 --check
[WARNING] "install.wim" does not contain integrity information. Skipping integrity check.
Calculating integrity table for WIM: 1019 MiB of 1019 MiB (100%) done
Calculating integrity table for WIM: 1005 MiB of 1005 MiB (100%) done
Calculating integrity table for WIM: 951 MiB of 951 MiB (100%) done
Calculating integrity table for WIM: 986 MiB of 986 MiB (100%) done
Calculating integrity table for WIM: 1020 MiB of 1020 MiB (100%) done
Calculating integrity table for WIM: 1023 MiB of 1023 MiB (100%) done
Calculating integrity table for WIM: 345 MiB of 345 MiB (100%) done
Splitting WIM: 6363 MiB of 6363 MiB (100%) written, part 7 of 7
Finished splitting "install.wim"
real 0m31,255s
user 0m27,026s
sys 0m4,223s
After waiting for 30 seconds (I have a fast NVMe drive) the "install.wim" file was split and I could remove it. Now the sources folder was ready to be copied onto the FAT32 partition of my USB drive (that has a GPT partition table). Next I rebooted, chose the USB drive in the Boot menu and the Windows 11 installation started (without the need to disable "secure boot").
On Windows you can split the install.wim file into smaller ones using the DISM.exe tool. Like on Linux you need to mount the ISO file and copy all contents to a folder on the hard disk. Next you need to start an elevated command prompt in that folder to use DISM command. Run the following DISM command:
dism /Split-Image /ImageFile:install.wim /SWMFile:install.swm /FileSize:1024
After splitting has finished you can remove the original install.wim file. The created SWM files (install.swm, install2.swm) will all be smaller than 1 GiB and can therefor be copied without errors to a FAT32 formatted USB drive.
On Windows you can use Rufus to create a bootable USB drive directly from the ISO file without you having to worry about anything. It will create a FAT32 EFI partition containing an NTFS driver and it will install from NTFS. Note that when selecting a Windows 11 install image it will also allow you to bypass the TPM check and set other nice things.. try it!
Rufus - Create bootable USB drives the easy way
During the installation press Shift-F10 and a Command Prompt window will appear. You can type the following commands:
reg add HKLM\SYSTEM\Setup\LabConfig /v BypassTPMCheck /d 1 /t reg_dword /f
reg add HKLM\SYSTEM\Setup\LabConfig /v BypassSecureBootCheck /d 1 /t reg_dword /f
reg add HKLM\SYSTEM\Setup\LabConfig /v BypassRAMCheck /d 1 /t reg_dword /f
reg add HKLM\SYSTEM\Setup\LabConfig /v BypassStorageCheck /d 1 /t reg_dword /f
reg add HKLM\SYSTEM\Setup\LabConfig /v BypassCPUCheck /d 1 /t reg_dword /f
Now the installer will install Windows 11 without hardware checks. When it asks to connect to a network type the following command:
start ms-cxh:localonly
You can now enter only a username and leave the password field(s) empty.
After doing this you can uninstall everything on the start menu and from "add or remove programs" that Microsoft allows you to uninstall. No worries, it won't allow you to uninstall things that are needed for normal operation of the operating system. In the latest Windows 11 (25H2) release you can even uninstall Edge and OneDrive! I recommend installing the following alternatives:
Windows 11 is not very privacy friendly, but this can be improved with a tool called "O&O ShutUp10++". Download and install "O&O ShutUp10++" and choose "Apply only recommended settings" and manually click the option "Disable extension of Windows search with Bing". The (recommended) option "Disable Windows Copilot+ Recall" is the most important one. If you don't disable this Windows 11 will send constant screenshots to Microsoft to profile what you are doing on your PC.
O&O ShutUp10 - Free antispy tool for Windows 10 and 11
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