Create Bootable USB For Windows 10 Install.wim Larger Than 4GB

How to Create Bootable USB For Windows 10 Install.wim Larger Than 4GB

The days of burning operating system ISO images to a disc are long gone. Today most PCs can boot from USB so it's just easier to update and more convenient to install Windows from a USB flash drive. Another good reason to install this way is the installation speed, which is significantly faster than setup running from an optical drive. Many modern devices do not come with an optical drive.

There are a number of methods we have already covered here, including Rufus for UEFI, the classic DiskPart, and PowerShell.

However, if you have an install.wim file in your Windows 10 distribution which is larger than 4GB in size, you may need to take extra steps to create a bootable USB drive. Your flash drive must have two partitions instead of the single one.

  • One of them must be formatted in FAT32. This will allow you to use the flash drive for both classic BIOS and modern UEFI devices.
  • The second one must be formatted in NTFS. It will be able to store large files.

Before proceeding, backup any important data from you flash drive. The procedure will erase all files and folders from it.

The steps below assume that you already have a Windows distro, and you are able to mount it in order to copy its files.

To Create Bootable USB For Windows 10 Install.wim Larger Than 4GB,

  1. Connect you flash drive to the computer.
  2. Press Win + R on your keyboard and type diskpart into the Run box. Hit the Enter key.
  3. In the DiskPart console, type list disk. It will show a table with all your disks, including the currently connected USB stick. Note the number of the USB stick drive. For example, it is Disk 1.list disk
  4. Type sele disk #,where # is the number of your USB stick drive. For our example the commands is sele disk 1.
  5. Type clean to erase the drive contents.
  6. Type create partition primary size=1000 to create a new partition of 1GB.
  7. Type create partition primary to create yet another partition that will take the rest of the remaining drive space.
  8. Type select partition 1 to select the first (1GB) partition.
  9. Format it in FAT32 as follows: format fs=fat32 quick
  10. Assign it the X letter: assign letter=X.
  11. Make it bootable with the command active.
  12. Now, select the second partition: select partition 2.
  13. Format it in NTFS: format fs=ntfs quick.
  14. Assign the Y letter to the second partition with the command: assign letter=Y.
  15. Leave DiskPart with the command exit.

You are done with the flash drive layout. The drive X: is a bootable small partition, and the drive Y: is a large NTFS partition to host the install.wim file.  Now, let's copy Windows files properly.

Copy Windows Setup Files

  1. Open your Windows setup files in File Explorer.
  2. Copy everything except the sources folder to the X: drive (the FAT32 one).
  3. Copy the sources folder to the Y: drive (the NTFS partition).
  4. On the X: partition, create a new sources directory. It will contain a single file, boot.wim.
  5. Copy boot.wim from Y:\sources to X:\sources.
  6. In the Y:\sources folder, create a new text file with the following contents:[CHANNEL]
  7. Save it as ei.cfg.

You are done. We have created 2 partitions: A FAT32 partition (X:) and an NTFS partition (Y:). We have placed the sources folder on Y:. On X: we store everything else of the original distro. We have also created a new sources  folder on X: with a single file BOOT.WIM. The last step is required to start the setup program when booting from our USB drive.

Now you will be able to install Windows using the flash drive you just created without reducing the install.wim file size. This is useful when you have a customized large install.wim file.

That's it.

5 thoughts on “Create Bootable USB For Windows 10 Install.wim Larger Than 4GB

  1. Viking

    I used the program “ISO2USB” to make bootable USB disk for Windows 10 version 1909 and I can easily choose whether to boot BIOS or UEFI.
    I have used this USB stick to boot more than 100 computers (HP, Lenovo and Dell). Never had any problem to choose boot mode. The USB stick has a single FAT32 partition and is MBR formatted.

    1. Sergey Tkachenko Post author

      A FAT32 partition cannot have files larger than 4GB. This works well for default install.wim.
      A custom wim file can include extra apps and drivers. It may not fit on FAT32.

  2. Danielx64

    Do you need to disable secure boot for this? I am aware that some 3rd party tools can do this but they require secure boot to be off to boot from the USB drive.

    1. Sergey Tkachenko Post author

      No, disabling secure boot is not required. You are using the signed Windows bootloader in this case.

  3. CarlS

    The Rufus FAQ says:

    “UEFI does NOT force the use of FAT32 for boot. As a matter of fact, you can just go out there and buy an Intel NUC PC, and you’ll find that it’ll boot an NTFS drive, in pure UEFI mode, just fine, with no need whatsoever for a FAT32 partition to exist anywhere.”


    Conclusion: A bootable WIM larger than 4GB should work on an NTFS-formatted flashdrive.


Leave a Reply

Your email address will not be published. Required fields are marked *