Dual boot clean up RRS feed

  • Question

  • I have a dual boot Vista 64 (C:) and a Win 7 64 (D:)  I have changed active drive to D: and moved the bootmgr to D:  I removed partition info from C: and rebooted...  All is well so far.  I want to move the Win 7 working install on the D: partition to the C: partition.   I am making room for the addition of Win 8 for testing purposes.   Single drive     I understand a considerable number of critical files are pointed to the D: partition currently and simply changing the drive letter will cause me grief.   Anyone have any suggestions or ideas...  I have most of the geek tools, so fire away.  Ultimately I do not want to have to reinstall Win 7
    Wednesday, September 21, 2011 12:57 AM


  • We don’t recommend you to perform this as this may cause a lot of issues. I have tested locally, after I changed the drive letter, I can’t log in to the machine.

    If you really need to do that, please backup all your files and prepare a Windows 7 DVD for repair if we need that.

    I think you can follow the following steps to do it:
    1. Current situation and the goal:
    a. Now the current drive letter on your machine:
    C: Windows Vista 64 bit
    D: Windows 7 64 bit

    b. Goal:
    C: Windows 7 64 bit
    D: Windows Vista 64 bit

    2. Boot to Windows 7, open the following registry path:

    3. Right click on “MountedDevices”, check if Administrators have full control. If not, change it to full control.

    4. Check the system drive letter in Windows Explorer, record it:


    5. Locate “\DosDevices\D:“ under HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
    Note: Maybe on your machine the drive letter is not D, for example, it’s X:, then the name would be “\DosDevices\X:”

    6. Check if you have “\DosDevices\C:” under HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices, if you have that, please right click on it and choose “Rename”, temporarily change it to “\DosDevices\Z:”. If not, please go to the next step.

    7. Please right click on “\DosDevices\D:“, choose “Rename”, change it to “\DosDevices\C:”.

    8. Change “\DosDevices\Z:” to “\DosDevices\D:“.

    Now we have completed the drive letter change, but after you restart the machine, it will fail to log on to the desktop. So we need to perform the remaining step.

    9. Please locate the following registry key:
    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\Current Version\Winlogon\Userinit:Reg_SZ:C:\Windows\system32\userinit.exe

    Note: the driver letter shown in the registry key should be the one that you see in Windows Explorer in step 4, the following is mine:


    Please change it to “C:\Windows\system32\userinit.exe”.

    Now the reboot will be successful and you will see your desktop.
    The drive letter now will be C: for Windows 7 and D: for Windows Vista.

    Please refer to the following Microsoft article for more detailed information though they are old and I have changed a lot:

    How to restore the system/boot drive letter in Windows




    Kevin Ni

    Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.
    • Proposed as answer by Kevin Ni-MSFT Wednesday, October 5, 2011 7:22 AM
    • Marked as answer by Niki Han Monday, October 10, 2011 3:23 AM
    Wednesday, September 28, 2011 8:05 AM