Windows 10: Enabling UEFI Mode AFTER clean install of Win10?

Discus and support Enabling UEFI Mode AFTER clean install of Win10? in Windows 10 Installation and Upgrade to solve the problem; I already did a clean install of Win10 on my Dell laptop which does seem to support UEFI mode when I went through the BIOS setup screen. My current... Discussion in 'Windows 10 Installation and Upgrade' started by win10freak, May 17, 2016.

  1. Enabling UEFI Mode AFTER clean install of Win10?


    I already did a clean install of Win10 on my Dell laptop which does seem to support UEFI mode when I went through the BIOS setup screen. My current BIOS setup is using the Legacy BIOS mode.
    My question is, if I do decide to enable UEFI with Secure Boot, will I need to reinstall Win10 again?
    If that's the case, then will I need to enable this UEFI before installing or after installing Win10?

    I installed Win10 using the Media Creation Tool.

    So does this mean that I have to start right from scratch again in order to use the UEFI with Secure Boot?
    In in other words, do I need to create another Media Creation Tool for my bootable USB flash drive and reinstall Win10 all over again?

    Or, can I just go into my BIOS setup and select UEFI with Secure Boot without reinstalling Windows again?

    Please explain this.

    :)
     
    win10freak, May 17, 2016
    #1

  2. Dell XPS 27 won't start - No Dell logo

    There is a known issue where a version Update can install a MS AHCI driver that toggles the UEFI BIOS from Legacy to UEFI enabled. To check for this enter BIOS setup per the suggestion in previous post to trigger F2 key at boot (using wired keyboard only),
    then confirm SATA controller is set to AHCI and check if UEFI mode is enabled, set it to Legacy or Both. Save settings and Exit to test.

    If nothing else works what always works is to
    Clean Install Windows 10
    after removing all other than target hard drive, setting BIOS to UEFI enabled with AHCI setting for SATA controller. Boot the provided media as a UEFI device, delete all partitions down to Unallocated Space. Stick with the rest
    of the steps, tools and methods in the link and you'll have the best possible install that will stay that way as long as you do.
     
    Greg Carmack - Windows MVP, May 17, 2016
    #2
  3. Windows 10 constantly rebooting

    Do you even have a UEFI BIOS? What are the UEFI settings in Setup?

    With UEFI enabled, or CSM or Both modes, you must boot Windows installation media as a UEFI device only, then delete all partitions to clear formatting and install.

    As to stray code affecting boot or performance, after troubleshooting countless thousands of these cases I would err on the side of having it correct if not optimal to avoid surprises.
     
    Greg Carmack - Windows MVP, May 17, 2016
    #3
  4. OldMike65 Win User

    Enabling UEFI Mode AFTER clean install of Win10?

    See if this tutorial helps you.
    https://www.tenforums.com/tutorials/2...tallation.html
     
    OldMike65, May 18, 2016
    #4
  5. My question is basically, that do I need to create another bootable USB Win10 ISO image with Rufus and reinstall Win10 again, or can I just enable UEFI without reinstalling again?
     
    win10freak, May 18, 2016
    #5
  6. OldMike65 Win User
    If you READ that Tutorial I posted the link for, it shows you how ....and answers your questions. Please read that tutorial.
     
    OldMike65, May 18, 2016
    #6
  7. Kyhi Win User
    YES and ENABLE BEFORE Installing..
    But you stated your PC does not support UEFI mode..
    So assume does not matter anyway..
     
  8. Enabling UEFI Mode AFTER clean install of Win10?

    My firmware does support UEFI mode, yes, but its not enabled.
    I just want to avoid creating a another USB boot media and reinstalling Windows again just to enable UEFI....
    And do I need Rufus for this or will the MCT will be enough for creating the ISO boot USB install media?
    And my BIOS already has been set to AHCI by default as per the link mentioned above.
     
    win10freak, May 18, 2016
    #8
  9. NavyLCDR New Member
    Media Creation Tool creates a USB flash drive that works with both UEFI and legacy bios.
     
    NavyLCDR, May 18, 2016
    #9
  10. Kyhi Win User
    The MS setup media supports both UEFI and Legacy booting and there is no need to use Rufus...
    If you plan on copying the contents from the ISO to USB - you have to format the USB > Fat32 < first... Again No need to use Rufus..
     
  11. Thanks a lot to all of you for the support.
    That's all I needed to know.
     
    win10freak, May 18, 2016
    #11
  12. I know I marked this as Solved, but this is just an Update

    Well I pulled the trigger on enabling uefi before reinstalling Win10 again. Here is what I did first.

    1 disabled legacy bios and legacy rom compatibility support mode
    2 selected enable uefi
    3 enabled secure boot
    4 reinstalled Win10

    The odd thing was that secure boot has to be left disabled before installing Windows but I enabled it before installing and no issues yet.

    And once secure boot is enabled, can I disabled it again?
     
    win10freak, Jun 11, 2016
    #12
  13. NavyLCDR New Member

    Enabling UEFI Mode AFTER clean install of Win10?

    Yes, you can disable secure boot at any time.
     
    NavyLCDR, Apr 4, 2018
    #13
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Enabling UEFI Mode AFTER clean install of Win10?

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