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May 25, 2020

USB install media with WIM file larger than 4GB

There’s nothing in the UEFI specifications that prevents booting from an NTFS formatted USB flash drive. In fact, this so-called limitation is entirely artificial. Luckily, most modern computers can boot from a single-partition NTFS formatted USB flash drive. Thus, one can indeed install Windows 10 from a custom WIM image larger than 4 GB, which is the the maximum file size on FAT32 media.

But, unfortunately, there are still a number of computers where BIOS / UEFI lacks proper drivers. That’s the real reason why they can only boot from FAT32. I have an Asus laptop: it’s only a few years old, and it simply refuses to boot from NTFS. Deploying my custom Windows image on that laptop from USB, I have been forced to split the 12 to 20 GB custom install.wim files that I create, so I can deploy them using DISM instead of running Windows Setup. For those interested in how to do this very thing, I’ve written a tutorial on TenForums.com.

Early this morning I had to make Windows 10 version 1803 multi edition USB install media. I had the Consumer Editions ISO, downloaded from my Visual Studio subscription, and I wanted to use this specific ISO. For this multi edition ISO, the install.wim file is annoyingly 0.03 GB too big to fit in FAT32 formatted USB flash drive:

OK, no problems, I thought, thinking that I would just split the WIM using DISM. However, knowing my friend for whom I was making this installer USB is not familiar with manually deploying from a split WIM, it would be easier for me to make the ISO bootable from a FAT32 partition. Then, he could run Windows Setup from an NTFS partition. Knowing his hardware, I suspected that at least on two computers he wants to reinstall he would not be able to boot from NTFS. So, I had to create FAT32 media to do the job instead.

The process is remarkably easy. Here is how I created Windows 10 USB install media which boots from a small FAT32 partition, then gives control to a larger NTFS partition which contains the 4GB+ install.wim file.

The first step was to remove the existing single FAT32 partition that used the full 8 GB capacity of the USB. Next, I created a 1 GB FAT32 partition and used the rest of USB’s capacity for an NTFS partition. I mounted the ISO, selected everything except the Sources folder, and copied these files and folders to the small FAT32 partition:

Now I created an empty folder on this FAT32 partition, labelling it Sources, and copied Sources\boot.wim file from mounted ISO to this folder:

Then I simply copied all of the ISO’s content, including the complete Sources folder to the bigger NTFS partition on the USB drive. Now I had a USB flash drive to install Windows 10 which boots from a small FAT32 partition, then runs Windows Setup from the bigger NTFS partition:

The difference between these two partitions is that on FAT32 partition, the Sources folder only contains one single file, the boot.wim file that’s required for the USB to be bootable.

That’s it. This USB flash drive can be used to boot any BIOS / MBR and UEFI / GPT computer. Because Windows Setup is run from NTFS partition, you can use this method for your custom install media with larger than 4 GB install.wim files.



Author: Kari Finn

A former Windows Insider MVP, Kari started in computing in the mid 80’s writing code for VAX / VMS systems. Since then, he’s worked in a variety of IT positions. He specializes in Windows image capture, customization, repair and deployment as well as Hyper-V virtualization. Kari is a proud Team Member at number #1 Windows site TenForums.com.

39 Responses “USB install media with WIM file larger than 4GB”

  1. August 30, 2018 at 15:13

    By the way, although this really is logical and easy procedure, I admit I had never thought to do it like this if not a fellow TenForums senior member Martin aka Cereberus had not suggested it in one of his posts on forums some half a year ago

    My post here is based on his post on TenForums: https://www.tenforums.com/tutorials/103340-dism-split-install-wim-file.html#post1282335

    I’ve used this method since reading it. Kudos where kudos belongs, thank you Martin!

  2. January 4, 2019 at 17:00

    Thank you so much… I knew it had to be possible, I came as far as copying everything to the NTFS partition, and everything except sources to the FAT32 partition. What I was missing was copying the boot.wim file to the FAT32 partition in the sources folder. That fixed it.

    The issue is that some standard Windows 10 ISOs now are too large to be burned to DVD, and for some reason the media creation tool failed to directly create bootable USB disks. (Win10, 1809, French downloaded directly from Microsoft is 5.1GB).

    Another advantage is that you can do all of this from the command line in Linux, which is my primary operating system. That makes my life so much more easy: it means I don’t have to use Windows (well at least on my own machines, I obviously still set them up for others)

    • January 4, 2019 at 21:58

      Good to know this method helped you!

  3. January 8, 2019 at 11:57

    Alas, I was a bit too enthusiast: I was in a hurry, saw it booted, considered it a success, and left this comment.

    On the machine I was installing HP ProBook 4340s, it booted and it allowed me to do the partitioning. After that, it failed with an error message. I presume it didn’t find install.wim, even though it was available on the NTFS partition.

    Given EFI spec doesn’t say that EFI partition must be FAT32, but that it’s the least that needs to be supported, I tried exFAT and NTFS partition, but the ProBook wouldn’t take them. Some EFI firmware does support NTFS, as I read. I presume that is what happened for you is that it booted from the NTFS partition because it could.

    In the end, I just gave up, booted a Windows PC and used Rufus.

    Rufus, has EFI bootloaders (that obviously need SecureBoot to be turned off) that boot from FAT32 and enable NTFS support. So basically EFI Firmware -> FAT32 UEFI:NTFS ( https://github.com/pbatard/uefi-ntfs ) -> NTFS partition containing the Win ISO files.

    I’m sure there must be a way to do this from the CLI on Linux: I’ll have to dissect what Rufus created to understand.

    So, sorry to disappoint you: your method seemed to work for me, but in the end it didn’t. However, it was informative and I do think there is not much missing to make it work.

    • January 8, 2019 at 12:38

      Sorry to hear that. I will check this further when I find some free time. Thanks for sharing your experience.

    • March 3, 2019 at 21:38

      I made an Ubuntu help page using this method starting with a compressed image file that sets up two partitions (one with FAT and one with NTFS). A grub bootloader in the head of the drive and grub files in the FAT partitions come with the compressed image file in order to boot in BIOS mode. Booting in UEFI mode works out of the box with Kari’s method, also with secure boot (I have tested it).

      There were some problems that I think were caused by the way I created the FAT partition, but I could solve them by letting Windows format the FAT partition. Windows (and its installer too) can be quite finicky with the FAT format, and I suspect that it can cause problems also for other people who use linux.

  4. Anon
    February 20, 2019 at 18:25

    Did you have any free time to sort this out? I have a similar issue.

    • February 20, 2019 at 18:32

      No, I have found nothing. I use this method on my own machines, creating the install USB to be used on them. Only thing I can think of being even remotely connect to your issue is that I always disable Fast Boot and Secure Boot in UEFI settings before doing a clean install. If needed, I will then enable them again after the installation.

  5. Dobri Boyadzhiev
    February 21, 2019 at 11:24

    Perfect tutorial. Thanks!

  6. March 2, 2019 at 21:35

    Thanks, this method works for me (good for the computers, that won’t boot in UEFI mode from NTFS) 🙂

  7. March 3, 2019 at 21:40
  8. Triggerz
    April 3, 2019 at 17:48

    Thanks a million! After several attempts, I’m finally able to install Win10 Enterprise on Surface Pro 6!

    Have a great day!

  9. Patrick
    April 28, 2019 at 15:20

    Just had to do this for a Windows Server 2019 install, worked flawlessly!

  10. Robert French
    May 21, 2019 at 10:25

    Thank you. Great solution, I wanted to create a more up to date windows 10 installer however the install.wim/esd file went from 3.36GB to 4.47GB (1809) stock build number 17763.107 updated build 17763.503

    I would have thought NTFS would have worked but it wasn’t booting or showing in the list and this was on either a 7th or 8th gen processor. Perhaps Lenovo are behind the times or something.

    Splitting the file was by other option but the command https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/winpe–use-a-single-usb-key-for-winpe-and-a-wim-file—wim says the syntax is incorrect. But this is a way more elegant solution.

    • May 21, 2019 at 11:20

      About splitting the Windows image, it only works with WIM file. If you have an ESD file as your comment suggests, it can’t be split. This could explain your syntax error. ESD must first be converted to WIM.

      I’ve written these tutorials on Ten Forums, see if they can give you additional tips:
      Split WIM file
      Convert ESD file to WIM

  11. Robert French
    May 21, 2019 at 16:46

    I also automated the installation and oobe via https://www.windowsafg.com/index.html very neat easy solution.

  12. Christopher Booth
    July 25, 2019 at 01:41

    What software do you use to create the partitioned USB, so that both partitions are visible with a drive letter ?

    • July 25, 2019 at 02:29

      I do not use any special software. Just the native Windows Disk Management.

  13. August 5, 2019 at 00:58

    Thank you so much for this…hours of searching for bootable USB for Windows, almost crying at the amount of failures…This is such a straightforward fix!! Having installed Ubuntu after an apocolyptic wipe out all trace of Windows, I was horrified to find the very neat software my partner needs to use for work has very few Linux genius developers interested in it…and despite literally months of faffing, just can’t get it to work without him swearing at least a couple times a night!

    THANK YOU!! You’ve saved our relationship!!! 😉 🙂

  14. hanysung
    August 9, 2019 at 11:56

    All the ISO files I burned before were 2.2gb files,which I burned without any obstacles,and the Windows ISO files were downloaded from Microsoft,you can even download it from elsewhere.
    As for Windows installation program,get more:https://www.androidphonesoft.com/resources/create-windows-10-installation-media.html
    If about Windows iso burner,consider trying the Rufus it is very powerful.

  15. December 25, 2019 at 16:55

    Hello, thanks a lot for this tutorial.

    I followed all the steps in Ubuntu 18.04 and I installed Win10 in another machine without any issue.

  16. nik
    January 15, 2020 at 20:26

    refering to https://www.heise.de/ct/hotline/Install-wim-groesser-als-4-GByte-2852980.html
    1. copy all files on the data/ntfs-part
    2. copy only boot, efi, bootmr, bootmgr.efi to boot/FAT32-part.
    3. update the BCD
    set DRV_BOOT=e:
    set DRV_DATA=f:
    bcdedit /store %DRV_BOOT%\efi\microsoft\boot\bcd /set {default} device ramdisk=[%DRV_DATA%]\sources\boot.wim,{7619dcc8-fafe-11d9-b411-000476eba25f}
    bcdedit /store %DRV_BOOT%\efi\microsoft\boot\bcd /set {default} osdevice ramdisk=[%DRV_DATA%]\sources\boot.wim,{7619dcc8-fafe-11d9-b411-000476eba25f}
    bcdedit /store %DRV_BOOT%\boot\bcd /set {default} device ramdisk=[%DRV_DATA%]\sources\boot.wim,{7619dcc8-fafe-11d9-b411-000476eba25f}
    bcdedit /store %DRV_BOOT%\boot\bcd /set {default} osdevice ramdisk=[%DRV_DATA%]\sources\boot.wim,{7619dcc8-fafe-11d9-b411-000476eba25f}


    best regards

    • January 16, 2020 at 14:42

      Yes, it works, it’s just far more complicated and time demanding.

  17. January 18, 2020 at 16:41

    Hi. I just wanted to say thanks. You got me past a stuck point. This worked like a charm! ~ Bill

    • January 18, 2020 at 20:40

      You are welcome. Good to know it worked for you.

  18. Juan José Granda
    January 25, 2020 at 21:40

    Pretty helpful Thx ?

  19. Stuart
    January 27, 2020 at 09:59

    It also worked perfectly for me, so thank you. I wouldn’t have thought of this myself because I would have expected a link between the boot partition and the ntfs partition. How does it know to look there for the rest of the code?

  20. Lionel
    February 8, 2020 at 12:19

    Thanks, worked like a charm

  21. Fabler2
    February 23, 2020 at 16:02

    Tried it out on the latest insider .iso even though the WIM file was well below the 4GB limit and it worked like a charm with secure boot disabled. Thank you for the valuable info.

  22. don bright
    February 23, 2020 at 22:54

    Thanks for posting this. I did this inside Ubuntu using gparted and mount to read the windows 10 iso and copy the files off. It allowed an old Toshiba Satellite i5 from many years ago to boot the Windows 10 iso without a problem.

  23. March 7, 2020 at 10:01


    Thanks for these instructions. I started to follow them but then tried something different that actually worked really well for me and may help other users. All I did was create two USB install disks. One formatted using FAT32 and the other formatted using NTFS.

    I then boot using the FAT32 USB stick, when I get the error message associated with trying to load a file >4GB, I simply swapped the USB sticks around so the NTFS disk was being read instead.

    If you only have 1 stick, you can just reformatted it after the error to NTFS and copy the files across.

    Not sure if this will work for everyone, but it did for me!

    Thanks again, this article was really helpful!


  24. Lê Quốc Phòng
    March 10, 2020 at 09:09

    As I know, we need to install a boot loader to USB to make it boot. However, it was not mentioned here. I miss something or we don’t need a boot loader to make a USB boot nowadays. Thanks.

    • March 10, 2020 at 17:08

      You are correct: a boot loader is a key ingredient that makes media bootable in Windows 10. Examination of the boot files (usually a pair of root level files named bootmgr and bootmgr.efi) will show the hardware how to find the OS and start loading it. If Kari omitted to mention this specifically, it’s likely because he assumed readers would know this already. Thanks for pointing it out.
      Best wishes,

      • March 11, 2020 at 14:35

        No additional boot loader is required, that’s why I did not mention it. Windows 10 ISO contains everything required, following these instructions to the letter creates a bootable USB Flash Drive with smaller FAT32 formatted boot partition, and bigger NTFS formatted partition for installation files.

        Really, following instructions, no additional boot loader is required.

  25. Linux User
    March 27, 2020 at 22:16

    Using Linux to build the USB image and Windows installer was getting 0x80300024, installer couldn’t assign drive letter to Drive 1 (USB), so wanted to post the solution if others run into the same issue..

    When creating partitions with gdisk, I used ef00 (proper EFI System type) for the FAT32 partition, this caused the 0x80300024 error, had to use 0700 (Microsoft basic data) instead. The NTFS partition was already 0700.

    Second issue, I used “mkfs.ntfs” to create the NTFS partition. Windows apparently needs to be able to fix/repair this before it can actually use it. If the USB stick is readonly, or using through QEMU etc with readonly flag for USB image, Windows considers it “RAW” instead of NTFS.

  26. Mike
    May 11, 2020 at 20:04

    This solution worked great – thanks Kari! It was simple/easy to do, and complete. Was able to get my Dell boxes up and running in no time. Much appreciated!

  27. Alex
    May 19, 2020 at 02:12

    Followed these instructions to the T, and when it came to the NTFS install.wim file, the files appear to not exist… ie: windows installer doesn’t see the files in NTFS format. I took the drive out and checked they were there and they were still there, so tried again, can see all the files in the FAT partition but the NTFS partition file is blank on the installer. Tried a different USB drive, and tried re formatting and reinstalling files again on the various partitions… same issue…

    Anyone else have this problem?

    Can’t believe they make it this difficult… FAT is max 4GB so let’s make a file 4.6GB that has to be installed via FAT format…?! It’s mad.

    I still need help on this, if anyone has any ideas. Thanks!

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