Windows 10: Multiboot os changes all drive letters and names, causing mayhem on audio/video system

Discus and support Multiboot os changes all drive letters and names, causing mayhem on audio/video system in Windows 10 Installation and Upgrade to solve the problem; Hello I've partioned my Win 7 Pro C drive into two naming the new partition X Windows 10 Pro theres no issues with booting and both OS seem to be... Discussion in 'Windows 10 Installation and Upgrade' started by Teejay52, May 21, 2020 at 12:07 PM.

  1. Teejay52 Win User

    Multiboot os changes all drive letters and names, causing mayhem on audio/video system


    I've partioned my Win 7 Pro C drive into two naming the new partition X Windows 10 Pro theres no issues with booting and both OS seem to be fine, however not with disk letters and names.

    Theres seven drives, the two OS and the DAW programs digital audio workstation run fine, but ...! There five data drives that contain literally years of client audio and some video that equate to millions of files, a single grand piano virtual piano can contain thousands upon thousands of data/sound files so having hundreds of virtual instruments of all kinds along with multitrack recordings takes a lot of preparation, set up time and constant updating and tweaking over the years as one can imagine.

    After installing Windows 10, I immediately noticed that all the drive letters have been changed making it almost impossible to find the data files when a project is loaded into the DAW in the Windows 10 installation.

    Heres a screen shot from the win 10 and in 7 , as you can see, the drive letting has completly changed and if I change them, thos changes then show up in the windows 7 install and turns that into a mess!

    it takes a number of days to down load, re-install, register and up date the programs and data files so I really dont want to mess up the Win7 at all.

    Can anybody offer a quick and easy solution to this please? I need to get the Win10 disk setup to match the Win7 one.

    Thank you

  2. nanohead Win User

    Changing the system volume drive letter safe?

    It depends. Need some more information. Is your boot volume c: ? If so, then others can be changed around as needed, but there may be collateral damage. Usually, if there are pointers set in the registry, as long as you use the storage management plugin to change the drive letter assignments, most things should work.

    Trouble comes in the form of applications that keep file system information (folders, path names, etc) in files that are stored in directories during installation. Those usually cannot be changed easily, unless you know that they are there and where they are....

    What drive letters are you trying to change specifically, and what is the operating system
  3. JediNemo Win User
    User Folder Relocation - drive letter changed / can't log in

    Not sure if this is the best thread to post this in.

    Here's the scenario.
    You use the (amazing) folder relocation tutorial in this forum. The process succeeds and you have a wonderful stress free year in Windows 10. Then your motherboard fails and you replace it with a different brand. Suddenly, when you get booted back to Windows, you can't log in! You quickly realize it's because you set your 2nd hard drive to drive letter "D:", but when Windows reloaded the disk drives because of the hardware change, it assigned "D:" to the DVD drive, and now you are stuck!

    Fear not fellow tweakers, I put in the research and have the solution (this may be redundant from another post, tried to search originally but didn't find anything, so my apologies if duplicating).

    Quick detail: First, we are going to boot into the recovery console and use the command prompt. In the recovery console, please be aware that it uses a virtual drive "X:" as the OS drive. Your other drive letters will be changed. Then we will identify which drive letter your OS is installed on. Next we will find which drive letter your user profiles are loaded on. Then we will make registry edits to fix the drive letter changes. Finally a reboot and celebratory dance.

    Note: You will need an understanding of command line operations and registry editing. If you do not, please find that information first, I will assume you have this knowledge moving forward.
    Also, there are no screen shots. I'm sorry, I didn't think I would be posting this while I went through the process, therefore I have no screen shots to share. If anyone has to go through this, it would be great if you could share your experience and provide screenshots if available.


    Step 1: Boot into the Recovery Console and select the Command Prompt option.
    * If you don't know how, basic tutorial: Interrupt the boot cycle 3 times to activate the recovery consol. As the system boots, when you see the windows logo, simply do a hard reset. After 3 times, when the windows logo appears, it will say it is starting "Automatic Recovery". Once that is done, log in with the local admin account and it will (at least for me) automatically open a command prompt.
    * This can also be accomplished a number of other ways including the use of recovery drives, install media, etc.

    Step 2: If you are confident on which drive is likely which, you can skip to step 3. If not, you need to determine which drive is which in the registry. To do this you have to use a variety of steps.
    1. Find the original OS drive. In the command prompt, type the following command:
      bcdedit | find "osdevice"
      The command will return osdecice partition=*: where "*" will be the current drive letter.
    2. Now you need to find the drive that has the user profiles folder assigned, from your folder relocation. There are a few ways to do this, I will list one. Type "regedit" in the command prompt to open the registry editor.
    3. In the registry editor, navigate to HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
    4. In this part of the registry you will see all the drive letters assigned to various volumes. From step 2a, you'll know which volume would be your normal "C:" drive. Write down the hex code associated with that drive letter. Next, you need to determine which drive letters represent volumes on physically mounted drives, and which represent removable media. Not getting too technical, basically you just look for all the volumes that have a hex code length equal to that of the OS drive.
      1. For example, if in step 2a you discovered that your OS drive is assigned the letter "W:", then look at the entry with that drive letter assigned. The number of hex entries represents a volume on a physically connected drive. Find all the other drive letters that have an equal number of hex entries. Those are all volumes on physically connected drives.
    5. Explore each of those drive letters to find the one with the user profile folder.
    6. Do this by typing "dir *:" in the command prompt, where "*" equals the drive letter.
    7. Go back to the registry editor (regedit). Find the "DosDrive" key entry with same drive letter as in step 2e. Write down the hex code for that key entry.

    Step 3: Before we can make the necessary registry changes, you need to connect to a different registry, called a "Hive".
    1. This link has a more expanded explanation of what we are about to do.
    2. In the key folder pane (left pane) of the Registry Editor window, highlight the "HKEY_LOCAL_MACHINE" option.
    3. Next, click on "File" and chose the option for "Load Hive"
    4. You'll have a familiar "open" window, navigate to the os drive found in step 2a.
    5. Navigate to the windows\system32\config folder
    6. Select the "SYSTEM" file option, and click "OPEN"
    7. It will ask for a key name. This is a temporary name and thus doesn't need anything official. Make it easy to remember. I used: "Drive Letter Change". Then click "OK"
    8. Now you will see an option under HKEY_LOCAL_MACHINE for "Drive Letter Change" (or whatever you named it in the previous step.
    9. Open that new folder and navigate down to
      HKEY_LOCAL_MACHINE\Drive Letter Change\MountedDevices
    10. This will look similar to what you found in step 2d, with the notable difference being this is what Windows will look like when not in recovery!

    Step 4: Make the registry changes
    1. Delete every registry entry that either starts with \\??\ OR has a hex code LONGER than the physical drives (Step 2d).
    2. You should be left with \DosDevices\ keys with equal length hex codes.
    3. Find the key with the hex code that matches with the OS drive you wrote down in step 2d. Make sure it is assigned the drive letter "C:"
      1. There should be no change in this
    4. Find the key with a hex code that matches your user folder drive, you wrote this down in step 2f.
    5. Right click that key name and chose the option for "Rename"
    6. Change the drive letter to whichever drive letter is needed for your particular setup.
      1. When I did my folder relocation initially, I had set my user folders to be found on the D drive. So on this step I renamed the key from "\DosDevice\E:" to "\DosDevice\D:"
    7. Confirm there are no duplicate or conflicting key entries: each drive letter will be used only once.
    8. *NOTE* For THIS particular set of keys (MountedDevices), you can safely delete everything thing. Windows will re-initialize these values at boot if it detects drives that are unaccounted for. So, if you delete everything besides the C drive and your user profile drive, that is OK! Windows will reconstruct the missing keys for you. Once you can log in, you can use Device Manager to change drive letters at will. This IS NOT TRUE for all registry items.

    Step 5: Close the registry editor

    Step 6: Type "exit" at the command prompt

    Step 7: Click on the button for "Turn off PC"

    Step 8: Count to 10, take a deep breath, and turn the computer back on

    Step 9: Log into windows

    Step 10: Assuming Step 9 worked, celebrate in your preferred method. If step 9 didn't work, double check you followed my instructions. If not, shut it all down and go to the beach!
  4. Multiboot os changes all drive letters and names, causing mayhem on audio/video system

    changing drive letter

    Hi Cathie,

    Thank you for posting your query in Microsoft Community.

    I understand the inconvenience caused. I will be glad to assist you with this.

    The drive letters change automatically and alphabetically depending on the number of drives available in the computer. For example, if you connect another USB or drive to the computer, it would be named as I. This must be the reason why the letter got changed
    to H.

    To better assist you, do let us know if there is already a G drive in the file explorer.

    If not, you do have the option to change the drive letter through disk management according to your preference. Follow the steps below:

    1. Press Windows key + R to open the run command.

    2. Type diskmgmt.msc and press enter to open disk management.

    3. On the left hand side of the window, right click on the "H" drive and select "change drive letter and path".

    4. Click "change" and assign the preferred drive letter from the drop down list.

    5. Save the changes and restart the computer if necessary.

    Hope this helps.

    Let us know if you need further assistance. We will be glad to help.
    Wungraileng Vashi, May 21, 2020 at 12:09 PM

Multiboot os changes all drive letters and names, causing mayhem on audio/video system

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