Reinstalling Windows 7 on 7/10 dual boot breaks dual boot

  1. Carsomyr's Avatar
    Posts : 236
    Win10 Pro x64
       #1

    Reinstalling Windows 7 on 7/10 dual boot breaks dual boot


    I installed the 10 tech preview along side my win 7 ultimate, I reinstalled, the Windows 7 side of the HDD because after however many years the OS had a LOT of clutter, and even though windows update was a nightmare I finally got all the updates installed and only the necessary drivers/software installed for the upgrade. However reinstalling 7 ruined my dual boot, I can no longer boot into the 10 tech preview... I was on build 10166, and I only have an ISO of 10162 which fails on startup repair... need suggestions on how to fix the bootloader to see both OS!
      My Computers

  2. Slartybart's Avatar
    Posts : 3,502
    Win_8.1-Pro, Win_10.1607-Pro, Mint_17.3
       #2

    Carsomyr said:
    I installed the 10 tech preview along side my win 7 ultimate, I reinstalled, the Windows 7 side of the HDD because after however many years the OS had a LOT of clutter, and even though windows update was a nightmare I finally got all the updates installed and only the necessary drivers/software installed for the upgrade. However reinstalling 7 ruined my dual boot, I can no longer boot into the 10 tech preview... I was on build 10166, and I only have an ISO of 10162 which fails on startup repair... need suggestions on how to fix the bootloader to see both OS!
    This is a good MSDN topic:
    Adding Boot Entries (Windows Drivers)

    Read it and ask any questions, lots of members know this stuff and can help guide you if you need it.

    Make sure you're reading the information on BCDedit - that's the tool for Win7 and higher.
      My Computer

  3. topgundcp's Avatar
    Posts : 2,617
    MintMate19x64 Win10Prox64
       #3

    Boot into Windows 7. Open Disk Management and note the drive letter for Windows 10 then open Admin Command Prompt and type:
    bcdboot X:\Windows
    where X: is the drive letter of Windows 10 OS.
      My Computer

  4. Kyhi's Avatar
    Posts : 3,129
    Windows 3.1 to Windows 10
       #4

    topgundcp said:
    Boot into Windows 7. Open Disk Management and note the drive letter for Windows 10 then open Admin Command Prompt and type:
    bcdboot X:\Windows
    where X: is the drive letter of Windows 10 OS.
    yup -
      My Computer

  5. Carsomyr's Avatar
    Posts : 236
    Win10 Pro x64
    Thread Starter
       #5

    Thanks guys I knew it could be done I just forgot the commands to restore it :P
      My Computers

  6. Carsomyr's Avatar
    Posts : 236
    Win10 Pro x64
    Thread Starter
       #6

    Ok. So apparently last night (While I was quite intoxicated :P) I tried to run the automatic repair thing on the windows 10 installation CD which failed. Now it won't boot to 7 or 10. So Now I'm running the cmd prompt off the 10 boot cd, trying to use the bcdboot command, and I get "Failure when attempting to copy boot files." Now what??

    EDIT: Currently loading my Win7 CD to try and fix that one first instead.
    EDIT2: Successfully repaired Windows 7 Boot config. Trying to repair 10 as suggested by topgundcp.
    EDIT3: Successfully repaired Windows 10 Boot config, dual boot menu is back. Thanks topgundcp And I'm a little curious why it didn't work from the 10 CD but at least for me it doesn't really matter. Remarking thread as solved!
    Last edited by Carsomyr; 12 Jul 2015 at 09:45.
      My Computers



  7. Posts : 3
    W01, W8.1,W7
       #7

    I typed in the bcdboot F:\Windows and got the message
    "Failure when attempting to copy boot files"

    If these are damaged or missing is there a way to correct this?

    Edit 1 - should add that previously before trying the bcdboot command I could not boot into either. Used the W7 installation disk to do start up repair. This fixed W7 but in msconfig boot only the W7 system showed.
    W10 is in disk management as healthy, primary with letter F.
    Last edited by dsim; 28 Jan 2016 at 22:10.
      My Computer

  8. cereberus's Avatar
    Posts : 11,410
    Windows10
       #8

    dsim said:
    I typed in the bcdboot F:\Windows and got the message
    "Failure when attempting to copy boot files"

    If these are damaged or missing is there a way to correct this?

    Edit 1 - should add that previously before trying the bcdboot command I could not boot into either. Used the W7 installation disk to do start up repair. This fixed W7 but in msconfig boot only the W7 system showed.
    W10 is in disk management as healthy, primary with letter F.

    I find it is easier to use Macrium Reflect Free sometimes to sort out dual boot.

    Install Macrium Reflect Free, create a bootable USB rescue drive.

    Boot from Rescue drive, and select restore tab, and click 'fix windows boot problems'

    It should list both OS's.

    Then click next, finish and it will rebuild boot sectors and create a dual boot menu for you.

    Then you can run msconfig to select which one you want as the default.

    Note : Macrium is on the Winpe Recovery iso in the app section if you prefer to use that (lots of great tools).
      My Computer


  9. Posts : 3
    W01, W8.1,W7
       #9

    Thank you cereberus.
    Unfortunately I have already tried my Macrium Reflect disk. I selected W10 and ran the repair, but on Restart only W7 showed.
    Both systems show in Disk Management - W10 as a Healthy, (Primary partition). W7 Healthy(Boot, Page File, Dump, Primary Partition)
      My Computer


  10. Posts : 3
    W01, W8.1,W7
       #10

    dsim said:
    Thank you cereberus.
    Unfortunately I have already tried my Macrium Reflect disk. I selected W10 and ran the repair, but on Restart only W7 showed.
    Both systems show in Disk Management - W10 as a Healthy, (Primary partition). W7 Healthy(Boot, Page File, Dump, Primary Partition)
    Edit 1 Have decided probably easier to reinstall W10 from disk, and will do this
      My Computer


 

Related Threads
Our Sites
Site Links
About Us
Windows 10 Forums is an independent web site and has not been authorized, sponsored, or otherwise approved by Microsoft Corporation. "Windows 10" and related materials are trademarks of Microsoft Corp.

Designer Media Ltd
All times are GMT -5. The time now is 04:31.
Find Us




Windows 10 Forums