1.    04 Jun 2016 #1
    Join Date : Apr 2016
    Posts : 4
    Windows 10

    System booting from wrong drive after installing new parts


    So I was booting Windows 10 from a drive labelled C: and all was well and good.

    Then I changed some parts around in my computer. Lo and behold, my computer is still booting the OS on C:, but from an unlabelled UEFI system partition on an external hard drive. Wat.

    I checked C:\boot, and there's nothing there. Startup repair does nothing, since it's properly booting after all (from the wrong place).

    I need to move this computer around, so leaving it the way it is is not an option. I've tried exporting the system bcd and putting it in C:\boot and marking the partition as active, but the bios still won't recognize the drive as bootable, so I'm assuming my MBR is toast. I'm also pretty sure bootrec is acting on the mysterious external system partition by default when I try to repair the MBR.

    I won't ask for a magic solution, since this is a pretty weird situation, but do you have any ideas of things I could try, or tools that would fix the MBR on the correct drive, or restore the stuff that should be in C:\boot by default?

    Thanks,
    Dright
      My ComputerSystem Spec
  2.    04 Jun 2016 #2
    Join Date : Aug 2014
    Forever West
    Posts : 3,984
    Win10 Home and Pro, Win10 Insider Preview, Win7 Home, Linux Mint

    Quote Originally Posted by Dright View Post
    So I was booting Windows 10 from a drive labelled C: and all was well and good.

    Then I changed some parts around in my computer. Lo and behold, my computer is still booting the OS on C:, but from an unlabelled UEFI system partition on an external hard drive. Wat.

    I checked C:\boot, and there's nothing there. Startup repair does nothing, since it's properly booting after all (from the wrong place).

    I need to move this computer around, so leaving it the way it is is not an option. I've tried exporting the system bcd and putting it in C:\boot and marking the partition as active, but the bios still won't recognize the drive as bootable, so I'm assuming my MBR is toast. I'm also pretty sure bootrec is acting on the mysterious external system partition by default when I try to repair the MBR.

    I won't ask for a magic solution, since this is a pretty weird situation, but do you have any ideas of things I could try, or tools that would fix the MBR on the correct drive, or restore the stuff that should be in C:\boot by default?

    Thanks,
    Dright
    Unfortunately, not knowing what parts you moved around makes it difficult to do a long-distance diagnosis but generally it doesn't take much to inadvertently plug the drive cables into a different controller port on the motherboard from what is was on when the OS was installed. When having such problems it is good to first unplug anything not needed such as external drives then try again.
      My ComputerSystem Spec
  3.    04 Jun 2016 #3
    Join Date : Jul 2015
    Posts : 9,551
    Windows 10 Pro

    A complete screen shot of disk management will help. Be sure to widen the columns so we can see all the information in them:
    Disk Management - How to Post a Screenshot of - Windows 10 Forums
      My ComputerSystem Spec
  4.    04 Jun 2016 #4
    Join Date : Apr 2016
    Posts : 4
    Windows 10
    Thread Starter

    I've attached the disk manager screenshot, and what I changed was the motherboard (and everything else except the disks).

    I managed to write a new MBR with bootsect, and my BIOS sees it as bootable, but it just gets stuck in a restart loop (just an underscore is displayed, no debug info).

    The main remaining problem in my mind is that c:\boot is empty.

    I have tried removing all other drives, but it won't boot without the external one.
    Attached Thumbnails Attached Thumbnails Capture.PNG  
      My ComputerSystem Spec
  5.    04 Jun 2016 #5
    Join Date : Apr 2015
    Posts : 12,952
    W10Prox64

    Hi,
    Here's a relatively painless way to correct partition problems:
    A Couple Questions About Partitions - Page 3 - Windows 10 Forums

    .
      My ComputerSystem Spec
  6.    04 Jun 2016 #6
    Join Date : Apr 2016
    Posts : 4
    Windows 10
    Thread Starter

    That looks good. I'll try it, and if it works, I'll mark this as solved. Thanks!
      My ComputerSystem Spec
  7.    04 Jun 2016 #7
    Join Date : Apr 2015
    Posts : 12,952
    W10Prox64

    Quote Originally Posted by Dright View Post
    That looks good. I'll try it, and if it works, I'll mark this as solved. Thanks!
    Good luck. Let us know how it goes.
      My ComputerSystem Spec

 


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