Can't boot in UEFI, only in Legacy, after clean W10 install from USB


  1. Posts : 111
    W10e
       #1

    Can't boot in UEFI, only in Legacy, after clean W10 install from USB


    Hey folks, i need your help (again)...

    I had to reinstall Windows 10 on an Acer Aspire. The "Upgrade Tool" failed repeatedly. I chose to install clean from an ISO to USB using Rufus.

    Not knowing the configuration of this laptop, i did a search and found instructions on how to boot from a USB drive, which had me change the CMOS(? F2 at startup) from UEFI to Legacy and use F-12 upon restart to select the USB drive for boot.

    Installed Windows 10 successfully.

    Boots fine in Legacy mode, but when i change it back to UEFI it gives me a "Boot device not found" or similarly worded error.

    Is there an easy fix?

    Thank-you! Much appreciate your advice.
      My Computer

  2.   My Computer


  3. Posts : 31
    Windows 10 Pro (10.0.18362)
       #3

    The question remains are you planning on using HDD larger than 2TB? If so then the only way to resolve is to reinstall Windows 10 with a UEFI partition setting and go from there. There is really no way around this. From what I have read.
      My Computer


  4. Posts : 111
    W10e
    Thread Starter
       #4

    Thank-you NavyLCDR! All working now, and Thank-You for your service!!!

    Thank-you Sawuwaya, i'm afraid i have nothing that large!
      My Computer


  5. Posts : 4,091
    Windows 7 HP 64 - Windows 10 Pro - Lubuntu
       #5

    To install win 10 as UEFI-GPT you must boot the installation disk as UEFI.

    Create a Win 10 installation disk.
    To prepare your USB flash disk, open a CMD window as administrator and type:
    Diskpart.exe (to enter diskpart)
    list disk (to list the computers disks. Take note witch number corresponds to your USB disk)
    select disk n (where n is the number of USB disk. Make sure to type correct disk number from step two.)
    clean (to erase all partitions on the selected disk)
    create partition primary (to create one partition on the selected disk)
    select partition 1
    format fs=fat32
    active (to make it Legacy boot able)
    assign (to assign a disk letter)
    exit (to exit diskpart)
    exit (to close the CMD window)

    Then all you have to do is to copy all iso files and folders to it.
    If your Win 10 iso has a \sources\install.wim bigger than 4G you will have to split it into smaller install.swm (Fat32 limitation)
    To do so, mount the iso file, go to \sources, garbagef +right click and select "Open Command window here" and on the CMD window type:
    Dism /Split-Image /ImageFile:install.wim /SWMFile:install.swm /FileSize:3600
    Two install.swm files will be created.
    Delete install.wim and then copy all files and folders from the mounted disk to the flash disk.
    It will boot as UEFI (If you have UEFI BIOS) or Legacy.

    Now set BIOS as UEFI. If it has a Fast boot and secure boot option, set it to disable.

    Boot the Win 10 installation disk as UEFI and install.
      My Computers


  6. Posts : 17,369
    Windows 11 Pro
       #6

    Sawuwaya said:
    The question remains are you planning on using HDD larger than 2TB? If so then the only way to resolve is to reinstall Windows 10 with a UEFI partition setting and go from there. There is really no way around this. From what I have read.
    Not true at all.
      My Computer


 

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