How to install two Windows OS's in same PC?

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  1. Posts : 19
    Windows 10 Pro
       #51

    NavyLCDR said:
    The second outcomes is that Windows Setup will create an EFI System Partition on Disk 1 which will boot only into Windows 11.
    Utterly unlikely, impossible with this partition in place. Antares, be a daredevil and proceed with installing.
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  2. Posts : 17,837
    Windows 11 Pro
       #52

    Volume Z said:
    Utterly unlikely, impossible with this partition in place. Antares, be a daredevil and proceed with installing.
    Certainly not impossible.
    Last edited by NavyLCDR; 29 Sep 2022 at 21:20.
      My Computer


  3. Posts : 19
    Windows 10 Pro
       #53

    There is no space available for an EFI System Partition on this disk.

    How to install two Windows OS's in same PC?-disk-1.png
      My Computer


  4. Posts : 17,837
    Windows 11 Pro
       #54

    Volume Z said:
    There is no space available for an EFI System Partition on this disk.

    How to install two Windows OS's in same PC?-disk-1.png
    Step #15 of our tutorial:
    Clean Install Windows 10

    How to install two Windows OS's in same PC?-capture.jpg
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  5. Posts : 19
    Windows 10 Pro
       #55

    That is not where antares is going to install Windows 11.

    antares said:
    if I reinstall Win11 in disk 1
      My Computer


  6. Posts : 223
    Windows 10x64 Pro
    Thread Starter
       #56

    Thanks NavyLCDR and VZ. If before clean installing Win11 on to Disk 1 I convert the dual boot to single boot first, by deleting the Windows 11 entry in the Boot section of msconfig followed by clean installing Win11 to Disk 1 (and then recreating the dual boot from within Win10 using msconfig), would that be a less risky procedure than simply clean installing Win11 on to Disk 1 without changing the current dual boot config?

    Of course I could be a daredevil as VZ suggests, by first backing up my current Win10 install
      My Computer


  7. Posts : 17,837
    Windows 11 Pro
       #57

    You really have nothing to worry about, as long as you select the correct disk to install to. Worst case scenario, you end up with a computer that will only boot into Windows 10 or Windows 11, and it is very easy to use the one simple BCDBOOT command to restore dual booting. More than likely, re-installing Windows 11 will just keep you dual booting in place. However it is NOT impossible for the new install to wipe out dual booting as VZ suggests. But if it does wipe out dual booting, it is a very easy fix.

    Now if during setup you click on the wrong disk to install to, you will wipe out the existing system that you want to keep.

    I don't know how many clean installs, especially on dual boot systems, that VZ has done, but I've done hundreds, if not thousands.
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  8. Posts : 223
    Windows 10x64 Pro
    Thread Starter
       #58

    NavyLCDR said:
    ...The solution if you lose the dual boot menu is to simply use the bcdboot command to add the opposite Windows installation to the boot menu.

    Code:
    Microsoft Windows [Version 10.0.22621.521]
    (c) Microsoft Corporation. All rights reserved.
    
    C:\Windows\System32>bcdboot /?
    
    Bcdboot - Bcd boot file creation and repair tool.
    
    The bcdboot.exe command-line tool is used to copy critical boot files to the
    system partition and to create a new system BCD store.
    
    bcdboot <source> [/l <locale>] [/s <volume-letter> [/f <firmware>]] [/v]
                     [/vbcd] [/m [{OS Loader ID}]] [/addlast] [/p] [/c]
    
      source     Specifies the location of the windows system root.
    
      /l         Specifies an optional locale parameter to use when
                 initializing the BCD store. The default is US English.
    
      /s         Specifies an optional volume letter parameter to designate
                 the target system partition where boot environment files are
                 copied.  The default is the system partition identified by
                 the firmware.
    
      /v         Enables verbose mode.
    
      /vbcd      Enables BCD logging.
    
      /m         If an OS loader GUID is provided, this option merges the
                 given loader object with the system template to produce a
                 bootable entry. Otherwise, only global objects are merged.
    
      /d         Specifies that the existing default windows boot entry
                 should be preserved.
    
      /f         Used with the /s command, specifies the firmware type of the
                 target system partition. Options for <firmware> are 'UEFI',
                 'BIOS', or 'ALL'.
    
      /addlast   Specifies that the windows boot manager firmware entry
                 should be added last. The default behavior is to add it
                 first.
    
      /bcdclean  Clean the BCD Store. By default, simply removes any duplicate
                 entries in the BCD. Can be followed by 'full'. In this case,
                 each entry is scanned. If the corresponding device for that entry
                 does not exist, the entry is deleted.
    
      /p         Specifies that the windows boot manager firmware entry
                 position should be preserved. If entry does not exist,
                 new entry will be added in the first position.
    
      /c         Specifies that any existing objects described by the template
                 should not be migrated.
    
    Examples: bcdboot c:\windows /l en-us
              bcdboot c:\windows /s h:
              bcdboot c:\windows /s h: /f UEFI
              bcdboot c:\windows /m {d58d10c6-df53-11dc-878f-00064f4f4e08}
              bcdboot c:\windows /d /addlast
              bcdboot c:\windows /p
    
    C:\Windows\System32>
    You mean use the bcdboot command using cmd from within the newly installed Windows 11?

    - - - Updated - - -

    NavyLCDR said:
    You really have nothing to worry about, as long as you select the correct disk to install to.

    Now if during setup you click on the wrong disk to install to, you will wipe out the existing system that you want to keep.
    That's exactly what I thought, when I start the fresh OS install by booting from the bootable USB created from the Win11 ISO, one of the first menus is indicating to which disk Win11 will install, and there should be both Disk 0 and Disk 1, and of course I would select Disk 1, so no chance of wiping Win10 in disk 0.
    By the way, should the dual boot menu be altered and Win 10 should remain invisible, what would be the exact bootcd command to run from cmd in Win11?
      My Computer


  9. Posts : 17,837
    Windows 11 Pro
       #59

    You would need to look at disk management and see what drive letter got assigned to the Windows 10 partition. Let's say it is E:. The command would be:
    bcdboot E:\Windows /d /addlast

    If you managed to boot back into Windows 10, then you would look at disk management and see what drive letter is assigned to Windows 11. It would be the same command, just using the Windows 11 drive letter.
      My Computer


  10. Posts : 19
    Windows 10 Pro
       #60

    None of this makes a difference. There is nothing risky about it no matter how you do it. If you take SIW2's advice

    SIW2 said:
    The simplest way is to format ( not delete ) the partition containing win11.
    even the touch of risk outlined by NavyLCDR can be ruled out. But most of all stop hesitating.
      My Computer


 

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