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There is a folder named $WINDOWS.~BT on the root of my C:\ drive. It is a hidden folder and is 75 MB in size.

What is its purpose? Is it safe to delete it?

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    Some files from that folder are even being executed by Windows, e.g. "Modern Setup Host" (C:\$Windows.~BT\Sources\SetupHost.exe) which tries to establish an Internet connection.
    – Jack Miller
    Aug 28, 2015 at 6:07
  • This is relatively funny: ➝ gizmodo.com/…
    – Frank N
    Jun 28, 2016 at 5:45
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    Mine is 4.7GB ^^U
    – David Gras
    Sep 25, 2016 at 22:58
  • I have this too. It showed after microsoft techs got into a remote session to fix some driver problems caused by Windows Update. This and a folder ESD were created around the time they were in a remote session on my machine. Of course the techs didnt fix anything and broke my video card drivers.
    – Ungeheuer
    Dec 17, 2016 at 5:11

2 Answers 2

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This seems to be Windows update logs & files.

It includes files to upgrade Windows, and also, once you do upgrade, the old OS goes into that folder

It should be perfectly safe to delete it, as long as you don't want to upgrade or downgrade Windows.

However, you can't do it the normal way.

Instead,

a) Press Windows key + R

b) Type: %windir%\system32\cleanmgr.exe

c) Hit Enter on your keyboard

Edit: This method seems to only delete some things in this folder, some may be left over. See the other answer for a more complete removal method, though that isn't perfect, either. Additionally, this may help: How to delete trustedinstaller files on Windows 8

Sources:

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    You should edit your answer to tell people that the windows 10 upgrade files are placed in this folder so you can upgrade from 7/8.1 -> 10. So deleting it will cause issues (or a re-download) of the Windows 10 upgrade files.
    – John
    Jul 29, 2015 at 19:54
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    ...and for those of us, who want to keep avoiding Windows 10, follow here: superuser.com/questions/922068/…
    – Frank N
    Aug 6, 2015 at 11:59
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    I have a hefty 4.7 GB “Windows 10 Preload” in that folder. CleanMgr.exe and manual deletion only gets as much as half removed. The rest can't be deleted for various lock reasons (even with UAC escalation priviledges...), in particular a Folder $Windows.~BT/Sources/SafeOS. Update: Taking ownership away from „Trusted installer“ partially helps: superuser.com/questions/497095/…
    – Frank N
    Aug 6, 2015 at 12:06
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    "Clean Up System Files" option on Disk clean up removed this folder
    – Alireza Fattahi
    Sep 16, 2015 at 13:50
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    OK, guys, since there seems to be a steady stream of new info for my answer, I'm going to convert to community wiki.
    – Quelklef
    Sep 18, 2015 at 4:36
42

Well, I got as much as 4.4 GB in it. Looks like Windows 7 is “pre-loading” Windows 10, though I never agreed and explicitly disabled it...

CleanMgr.exe mentioned in the other answer deleted some stuff, but mostly refused. Manual removal in File Manager also failed, because of lack of rights (even with full admin privileges), lack of ownership (owned by “TrustedInstaller”), etc...

Here is a brief receipe, to help yourself from windows command prompt with administrator rights:

// go inside that folder:
cd /d "C:\$Windows.~BT"

// take over ownership
takeown /f *.* /R /D Y

// (go for coffee, takes a minute)
// grant full rights to everyone
icacls *.* /grant Everyone:(OI)(CI)F /T

// (coffee?)
// and all other subfolders, just be careful with use of *, naturally.
rmdir Sources /s /q

// actually, I got a few errors with rmdir. Things went smoother 
// with this Unix-like ´rm´ executable in your path,
// coming from unxutils.sf.net
rm -r -f *

// after all has been wiped, also remove the parent dir

C:\$Windows.~BT>cd ..
C:\>rmdir "$Windows.~BT"

// checking...
C:\>dir /A:DHS
 Volume in drive C is Windows
 Volume Serial Number is ####-####

 Directory of C:\

15/07/2015  19:15    <DIR>          $Recycle.Bin
30/07/2015  16:39    <DIR>          Boot
04/08/2015  08:35    <DIR>          Config.Msi
14/07/2009  07:08    <JUNCTION>     Documents and Settings [C:\Users]
01/11/2012  09:35    <JUNCTION>     Dokumente und Einstellungen [C:\Users]
01/11/2012  09:35    <JUNCTION>     Programme [C:\Program Files]
04/08/2015  08:35    <DIR>          System Volume Information
               0 File(s)              0 bytes
               7 Dir(s)     ########### bytes free
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    While this doesn't answer OP's question, it is useful. You may want to consider making a "wiki question" with this.
    – Quelklef
    Aug 6, 2015 at 15:32
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    This is outrageous. I never wanted or agreed to some "pre-download" of Windows 10 to my hard drive, yet Microsoft think it's find to waste 4 GB of hard drive space anyway? And who's to say that if I delete it, their update system won't be abused to download the 4GB again???
    – Jez
    Aug 24, 2015 at 21:36
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    @Jez: Yes, neither did I. Personally I rate W10 use somewhere between drunk driving and hair-drying in the bathtub. And whatever privacy & security advocates dig up right now, serves me right very much...
    – Frank N
    Aug 25, 2015 at 9:41
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    My strategy: Hold to W7 as long as possible. Change to a new Linux-based host OS — after convert current W7 to a Virtual Machine (to keep legacy MS-only apps alive), i.e. using Macrium Reflect.
    – Frank N
    Aug 25, 2015 at 9:43
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    This is appalling. For the past week or so both our PCs have been sluggish and our internet connection has been very slow. Now I find 5GB in this folder on both PCs, so its downloaded 10GB! Without my authorisation. I love windows, and normally have no problems with MS, but this is just beyond a joke, they should not be doing this to millions of PCs around the would, just because they want to.
    – Rob Donovan
    Sep 20, 2015 at 8:55

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