What is in $WINDOWS. ~ BT that prevents Windows upgrades? How does removing the folder fix failed Windows upgrades? RRS feed

  • Question

  • What information is within the $WINDOWS. ~ BT folder that prevents Windows upgrades?

    How come removing the folder allows Windows upgrades?

    Is there any disadvantage in removing the folder?

    Should it be part of a step in the upgrade check list to fix failed upgrades?

    Saturday, March 31, 2018 12:48 PM

All replies

  • Is there any disadvantage in removing the folder?

    It would prevent automatic restart if an install failed.  The only reason I would delete it is if I needed the extra space it takes up.  Supposedly we can avoid that need by attaching a temporary drive.  I have seen the need and the prompt but at the time was in a VM and didn't know how to attach a drive on the fly.  I wasn't sure what I was going to do if the install failed but since it was only a VM I wasn't very concerned.

    The other thread you pointed out implied that size was not an issue, e.g. they were renaming the space which would require even more space.  Then the only thing I can think of is that perhaps the install takes note that there is no possibility of a restart and therefore makes extra effort to getting you somewhere useful.  This might be something that ProcMon could help you puzzle out.   ; )

    Robert Aldwinckle

    Saturday, March 31, 2018 5:33 PM
  • Hi,

    After you upgrade to Windows 10 you may notice two folders on your System or C Drive named $Windows.~BT and $Windows.~WS. These folders are created by Windows, during the upgrade process.

    As far as I know, it refers Windows Update error 0xc1420127 and 0xc190010b.

    An important folder within $WINDOWS~BT is the Panther folder, which keeps a black box recording of what happens during setup. If your computer experiences an unsuccessful installation then setup rolls back, you should check the setup error located there.

    You could delete the folder without no benefit other than occupying space on your hard disk.

    I consider that it's something like Windows Update softwaredistribution. After upgrade fail, we could delete or rename it to clear Windows Update cache.

    When a Windows 10 update has failed, you’ll find (some of) its files in a directory C:\$Windows~BT. Before trying the update again, the directory needs to be deleted – or if all else fails, renamed.


    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact

    Monday, April 2, 2018 9:52 AM
  • Hi,

    About C:\$Windows~BT directory, Carl Fan described in detail.
    So, I'd like to add some information to delete unneccssary folders/files.

    (1) [Settings] > [System] > [Storage] > [Change how we free up space]
    (2) check all items (in Temporary Files) > [Clean now]    

    # I have several virtual machined running Window 10 Insider Preview. They don't have much free space, and sometimes Windows Updating failed (e.g. Creators Update > Fall Creators Update).  Upgrading of version requires more than 15 GB of free space (from my experience).
    If free space of your storage (C drive) becomes less than 15 GB, please do [Clean now] before April 11 (Spring Creators Update). 


    Ashidacchi --

    Monday, April 2, 2018 11:54 PM
  • The deleting of the folder appeared to help at least 19 upgrade failures in the link.

    However the suggestion to delete the folder is not found in the upgrade failure troubleshooting steps or even as an intermediate or advanced step in troubleshooting.

    So it was found by trial and error or is there a Microsoft reference for the troubleshooting step?

    The step was used on drives that were not short on free space to troubleshoot the failures.

    Within the BT folder are numerous file types:







    windows performance analyzer  trace file

    cascading stylesheet

    Which file type can interfere with Windows updates?

    If an OP wants to keep the files that don't interfere with upgrades and delete the file types that can interfere with upgrades which file types need to be deleted?  Please explain.

    Tuesday, April 3, 2018 8:34 AM
  • Please use features built-in Windows, such as [Clean now] and [Disk Cleanup].

    Ashidacchi --

    Tuesday, April 3, 2018 8:39 AM
  • The methods to clean are known.

    Computers can use 3rd part software such as Ccleaner to remove or delete or clean files.

    The purpose of the thread is to learn or understand how the BT file may or may not impact upgrades when there is plenty of free space on the drives.

    With space constraints out of the picture what I am seeking is information about any files within the folder that can interfere with Windows 10 upgrades.

    Which file type and how can it interfere with the upgrade?

    Tuesday, April 3, 2018 8:56 AM
  • If sufficient free space is left, the BT folder has no impact to upgrading.

    Ashidacchi --

    Tuesday, April 3, 2018 9:01 AM
  • Please have a look at this thread:

    In the thread there are 19 at this moment that voted for the renaming of the BT file.

    The renaming of the file does not delete the old file and the space remains nearly the same or is slightly reduced.

    Somehow the renaming of the file fixed the upgrade failures.

    How did that happen?

    Which file or files interfered with the upgrade and how?

    Tuesday, April 3, 2018 9:10 AM
  • This link was found with comments on deleting $WINDOWS. ~ BT

    In the case of a failed upgrade, it is better to delete the folder and start the upgrade process afresh.

    There was no explanation of how it could increase the likelihood of success with the upgrade failure.

    It did not indicate the problematic file type or the problematic file.

    So it's still a puzzle how 19 people went from failed upgrade to upgrade success by deleting  $WINDOWS. ~ BT

    If anyone finds out please post the information.

    Wednesday, April 4, 2018 11:40 PM
  • Failure of upgrading has several causes. Insufficient free space is one of them.
    Deleting $WINDOWS.~BT cannot give assurance of successful upgrading.  

    Ashidacchi --

    Wednesday, April 4, 2018 11:48 PM
  • I agree that the presence of some folders seem to inexplicably cause feature upgrade installation attempts to fail. I think it may have something to do with preventing the accidental overwrite of backup files during immediate back-to-back upgrade installation attempts. In any case, if an upgrade is successful, then Microsoft Windows will automatically delete these folders after so many days go by. If there is no intent on rolling back an upgrade, it seems to me that it is safe to delete these files at any point in time. It would be nice if a new feature upgrade installation attempt would do this for us automatically or at least fail with a more obvious error message.

    For deleting the folders with Disk Cleanup:

    • C:\~Windows.BT 
    • C:\Windows.old

    Disk Cleanup --> Cleanup System Files. If available, choose options:

    • Windows Upgrade log files
    • Previous Windows Installations
    • Temporary Windows installation files

    I have sometimes noticed this complete with no error message, yet remnants of C:\~Windows.BT remain. If that's the case, then some files are probably still in use. Sometimes a reboot will help, sometimes not. In the cases where reboots won't help, drill down in to the C:\~Windows.BT folder to see which files are in use. You might be able to use Sysinternals handle to determine what is using the file. Or if the name of the file makes it obvious, you might have a corrupt installation. In my case, I had to uninstall Symantec Endpoint Protection and Citrix Receiver before I could delete C:\~Windows.BT.

    Monday, August 20, 2018 3:27 PM