What is the $WINDOWS.~BT folder?

Question

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?

Answer 1

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:

• http://answers.microsoft.com/en-us/windows/forum/windows_8-windows_install/how-do-i-delete-windowsbt-after-failed-windows-8/d15416e8-fd5a-4d4e-b04b-5907a4f6c623
• John (see comments)
• FranKee (see comments)

Answer 2

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