Windows 10: UEFI dual boot 2x WIN 10 Pro failing

Discus and support UEFI dual boot 2x WIN 10 Pro failing in Windows 10 Support to solve the problem; Dear all, I ll be the first to admit that I have created this mess, but now got so far stuck that I can't find a way out anymore. Any help is very... Discussion in 'Windows 10 Support' started by Bruxlux, Jan 11, 2021.

  1. Bruxlux Win User

    UEFI dual boot 2x WIN 10 Pro failing


    Dear all,
    I ll be the first to admit that I have created this mess, but now got so far stuck that I can't find a way out anymore. Any help is very welcome!

    What I did:

    1. I started with 2 perfectly running win 10 pro installations on 2 different drives ("Work" drive and "Play" drive), with every restart ending up at the WIN 10 UEFI Dual Boot Screen.
    2. Then I decided to reinstall the "Play" drive, so I deleted all partitions on this drive and installed WIN 10 Pro through my USB drive created with the Windows Media Creation tool.
    3. I now believe that this drive originally contained the Boot sector and had a GTP table.
    4. Upon restart I could only boot into the new "Play" drive, which was now in MBR table (MB is set to UEFI + CSM mode).
    5. I manged to rebuild the Boot sector on the "Work" drive with bootrec /FixMbr bootrec /FixBoot bootrec /ScanOs bootrec /RebuildBcd. Which allowed me to boot to both drives, but only by going into the boot menu (F12), so no DUAL Boot Screen.
    6. Running Diskpart I noticed that now both drives were in MBR. Thinking this might be an issue I converted both to GTP with the win 10 MBR2GTP commands.
    7. This didn't change anything either. On restart I didnt get any DUAL Boot screen and could only get to the "Play" drive by going into the Boot menu, or changing the Boot order in the BIOS.

    Now the real mess started:

    8. I then decided to install EasyBCD on the "Work" drive and added the to bootable drives. This worked ONCE. On restart I got the UEFI Dual boot screen and booted to the "Play" drive.
    9. Restarting from the "Play" drive however got me straight back to the "Play" drive and restarting from their did the same without any dual boot screen.
    10. Then I thought I ought to install EasyBCD on the "Play" drive as well, which I did.
    11. This resulted in No dual boot screen and trying to boot to the "Play" drive I got a No windows installation found
    12. Now desperate I ran an auto-repair from Easy Recovery Essentials on the "Play" drive. Upon restart I didn't get any dual boot screen and booting (F12) to the "Play" drive resulted in a BSOD stating, "inaccessible boot device".
    13.Checking the "Play" drive in Diskpart showed that Easy Recovery Essentials has converted the "Play" drive back to MBR.
    14. ... and that where I am at!!

    I feel I should just clean the whole mess up and rebuild the UEFI Boot sectors etc from scratch, but I don't know where to start now.

    So in short, I would like to be able to boot from the Win 10 UEFI Dual boot screen, showing both my Win 10 pro "Work" install and my Win10 Pro "Play" install, if that makes sense.

    Reinstalling the "Work" drive would only be a last last last resort option.

    Thanks!

    Maybe the below DISKPart / EasyBCD overview helps:


    UEFI dual boot 2x WIN 10 Pro failing [​IMG]


    Disk management etc - Album on Imgur

    :)
     
    Bruxlux, Jan 11, 2021
    #1
  2. JB1954BN Win User

    Dual booting with Win 10 Pro and Win 7 Pro

    I'll be receiving a new computer with Win 10 Pro as my computer w/ Windows 7 Pro crashed. I'd like to take the hard drive with Windows 7 Pro and install it into the new one to have dual booting. Any problem doing that and what steps are needed? Thank
    you.
     
    JB1954BN, Jan 11, 2021
    #2
  3. Dual booting Windows 7 Pro and Windows 10 on a UEFI Firmware

    I am having a new MSI GT72S Dominator Pro G-219 configured.

    6th Gen Intel Skylake Core i7-6820HK (Unlocked) , 2.7~3.6GHz CPU

    64 GB RAM

    2 PCIe 512GB SSDs in RAID 0

    2 M.2 500GB SSDs in RAID 0

    2TB 5400 RPM mechanical drive

    I would like to be able to dual boot Windows 7 Pro and Windows 10 Home.

    The computer has UEFI Firmware.

    I am just becoming familiar with UEFI concepts.

    I have been told that Windows 7 Pro runs in "BIOS Compatible" mode on the UEFI Firmware.

    And therefore the computer cannot be setup to dual boot both Windows 7 Pro and Windows 10 Home.

    I will be using this computer for data processing and Windows 7 Pro is

    much simpler and better to use to quickly set up process flows for complex data processing tasks.

    Windows 10 is very bad for doing this kind of work.

    We can discuss why that is somewhere else.

    My question is: can I set up this computer to dual boot Windows 7 Pro and Windows 10 Home.

    I would very much appreciate expert knowledge and steps on how to accomplish this.

    Thank you

    Robert Lorbeer

    *** Email address is removed for privacy ***

    <PII- Removed>
     
    RobertLorbeer, Jan 11, 2021
    #3
  4. UEFI dual boot 2x WIN 10 Pro failing

    dual boot windows xp with uefi windows 10

    Hi,

    It definitely is possible to do a dual boot of Windows 10 with a older version of Windows. There are several steps involved to successfully achieve your objective. For us to resolve your concern, we suggest you follow the step by step process provided by
    Andre Da Costa in the article:
    How to dual boot Windows 10 and older versions of Windows
    .

    This covers installing different versions of Windows alongside Windows 10 in a dual boot environment. Take note though to backup any important files that you have before proceeding with any of the steps to prevent any data loss.

    We look forward to your response once you complete the steps.
     
    Jordan Dom, Jan 11, 2021
    #4
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UEFI dual boot 2x WIN 10 Pro failing

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