Windows 10 2004: Upgrade fail due to drive letter on boot partition

[German]German blog reader Tibor simandi Kallay has sent me an e-mail alert about a problem when upgrading to Windows 10 May 2020 Update (version 2004). The upgrade fails at 30% of the installation with a message about invalid registry paths. Here is a description of the problem and the solution.


The error description

Tibor simandi Kallay wrote in his mail: On a number of my PC's there was a strange error when upgrading to Windows 10 version 2004. The partition "System-reserved" contains the boot manager (cmd as admin, bcdedit) and at the same time this partition is assigned a drive letter (B:). Furthermore this partition is active so that the system can boot from it.

Tibor simandi Kallay could not find out why the partition has a drive letter – but there have been updates in the past that assigned a drive letter to the partition.

But when upgrading an existing Windows 10 to the May 2020 Update (version 2004) the process failed. After copying the files, Windows must install the updates. This is indicated by a display in Windows PE in white letters on the blue background. During the message "Updates are processed 30%" the following error message has been shown:

"The system registry contains invalid file paths. Installation cannot proceed. This system image was applied without guaranteeing that drive-letter assignments would match across computers."

If the user clicks on Okay. this leads to a restart and the message appears:

Any changes made to the computer will be undone…

After half an eternity a restart occurs and after that the user will find his old Windows installed again.


The solution for the upgrade problem

An administrator must delete the drive letter of the System Reserved partition before upgrading. This can be done from the Disk ManagementChange Drive Letter or Path branch in Computer Management. Then the upgrade should go through without problems.

Furthermore Tibor simandi Kallay wrote to me: By the way, it's good that even PCs which are not yet offered the upgrade will survive the procedure without any complaints if the update is done with the Microsoft Update Assistant, which can be downloaded here. Of course you should do the usual things before that:

    check all media
    Drive C: Clean up
    execute sfc /scannow
    DISM /Online /CleanUp-Image /RestoreHealth

Unfortunately, Microsoft never checks the last point in particular. However, you can do this as a user by right-clicking on the My Computer icon and selecting Properties from the context menu. In Advanced System Preferences, select the Environment Variables button. In the displayed dialog box the entry Path can be selected under the category System Variables.

Via the Edit button a dialog opens in which the value of the variable can be adjusted. Sometimes you will find entries that no longer exist or duplicate entries, writes Tibor simandi Kallay. These should be checked or removed before the upgrade. At this point I would like to thank the blog reader for pointing this out, maybe he helps those affected.

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11 Responses to Windows 10 2004: Upgrade fail due to drive letter on boot partition

  1. Chris Pugson says:

    A problem with restart of the system after failed updates is that System File Checker is likely to find corrupted files (in the restored previous system version which failed to be upgraded) which it does not fix.

  2. wyxchari says:

    And yet another failure on all my computers: C:\DumpStack.log.tmp

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\CrashControl DW EnableLogFile 0
    Restart and delete.

    Congratulations Microsoft for working so well. XDDDD

  3. Alberto says:

    Hello, during the upgrade to Windows 10 2004 the second time that my machine rebooted the message : "boot device found Press any key to reboot the machine" appeared and I was not able to get rid of it, I tried different hard drives, download windows from external flash drive , bios settings, bios upgrades …. the PC was two month old, then I had to send it back to my provider …in my opinionion must be something related to the upgrade.

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  5. Nancy says:

    YES!!! This worked!!!
    After many attempts this made the upgrade to Windows 10 possible.

  6. Martin says:

    I had the same thing happen trying to upgrade an old laptop from Windows 7 Pro to Windows 10 today. I checked and there was no letter on the Reserved Partition so I put one on, then deleted it to be sure, then tried the update again, and got the same result. There must be other reasons for this error as well.

  7. John says:

    I created the bookable disk but still got the error after a very long process. I have no drive letter in the system partition. Not sure what to do next.

  8. Phil Reinemann says:

    In the last 6 months (since June 2022) we have experienced "registry contains invalid file paths" when upgrading from W10 20H2 to 21H2.
    This worked on at least 5 (Dell Latitude E5450) laptops, but it depends on physical access to battery.

    Remove AC power from the laptop.
    Access the battery and disconnect it or remove it.
    Hold down the power button for >=11 seconds. (May not be necessary but the time to do this allows for circuits to drain.)
    Run your upgrade (update).

    As near as we can tell, something in the BIOS preserves some info (like drive letter assignments) that gets reset by removing power.

    Let me know if the above works for you too.

  9. fuer sonstiges says:

    This sentence "Unfortunately, Microsoft never checks the last point in particular." makes no sense because after the row
    – DISM /Online /CleanUp-Image /RestoreHealth
    the next and last row (copied from the GER site)
    – die Pfadangaben auf nicht mehr vorhandene oder doppelte Einträge prüfen.
    is missing!

    P.S. I got the same "… registry contains invalid file paths." error at a Win10 V20H2 to Win10 V22H2 upgrade try, until now nothing helped.

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