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Unable to create bootable USB for Windows 10 Enterprise with Windows 10 20H2 iso

Anonymous
2020-10-22T16:17:02+00:00

I am creating a Bootable USB to boot UEFI enabled computer with Secure Boot ON. This requires that the USB is formatted with FAT32. FAT32 partitions cannot handle files bigger than 4.00GB. Windows 10 20H2 Business Editions iso has multiple edition baked into one ISO. And hence the file size of "sources\install.wim" is larger than 4.00GB. 

For this I used dism tool to extract image for specific edition from the "sources\install.wim", and then use the extracted image in bootable USB. Extracted image was always less than 4.00GB, which was good to store on FAT32 filesystem.

For Windows 10 20H2, extracted image for enterprise edition is 4.34 GB (4,559,417 KB which is larger than 4.00 GB). And hence cannot be stored on FAT32 filesystem, which in turn is not allowing me to create a bootable USB to install Windows on machine with UEFI enabled and  with Secure Boot ON.

Windows for home | Windows 10 | Install and upgrade

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  1. Anonymous
    2020-12-29T19:29:01+00:00

    The UEFI specification specifies that it can load EFI boot files from FAT partitions. So all UEFI BIOSes must contain a driver which understands the FAT file filesystem so that it can load the boot file (default file is \EFI\BOOT\BOOTX64.EFI for an x86 64-bit UEFI BIOS).

    Now some UEFI BIOSes also contain a driver for the NTFS filesystem (e.g. some ASUS BIOSes, etc.). This additional driver is optional - some BIOSes will have it and some won't. Thus being able to UEFI64-boot from an NTFS partition depends on whether the system's UEFI BIOS contains the extra NTFS driver and so can load the .EFI boot  file from it.

    Rufus adds a 2nd FAT partition with a UEFI boot file which contains the extra NTFS driver and then it loads the Windows boot files from the first NTFS partition. However, the Rufus boot files are not signed and so you need to disable Secure Boot.

    If you must keep Secure Boot enabled, you could try preparing an Easy2Boot USB drive (made under Win10 and including the agFM UEFI boot files). After making the E2B USB drive, copy over the large Windows Install ISO to the \_ISO\WINDOWS\WIN10 folder - then UEFI64-boot to the 2nd UEFI FAT32 partition and use the menu system to select the ISO. E2B+agFM uses the Kaspersky shim which is signed, so it usually works unless your UEFI BIOS specifically blocks that shim boot file.

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  2. Anonymous
    2020-10-28T19:41:30+00:00

    However, with same steps, I cant boot my Surface device from NTFS formatted USB (BIOS Mode is UEFI and Secure Boot State is ON).

    It is documented here that you will have to use FAT32 formatted USB to boot Surface device from USB.

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  3. Anonymous
    2020-10-22T17:09:00+00:00

    Based on this document Bootable USB should be formatted as fat32 for UEFI.

    I created a USB with NTFS filesystem using the same document that I linked. I was able to boot my UEFI Enable/Secure Boot On using the NTFS formatted USB. This is great.

    Thanks for help.

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  4. Anonymous
    2020-11-01T15:12:19+00:00

    I have a similar but different issue.  My 10 year old desktop has a “unmountable bootvolumn error”.  I am trying to create a bootable usb using a Microsoft Surface.  The instructions say to go to “download” and then direct where you want the file saved to.  When i click on download it automatically downloads and saves to the C: drive.  I do not have the option to redirect to the usb.

    how do i resolve this.

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  5. DaveM121 888.7K Reputation points Independent Advisor
    2020-10-22T16:26:28+00:00

    Hi Bhavesh

    I am Dave, an Independent Advisor, I will help you with this . . .

    The USB does not need to be formatted as FAT32, in fact the preferred file system is NTFS for a bootable Windows 10 USB to install on a UEFI system, for example, using Rufus, these would be the default settings to create the bootable USB:

    .

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