If you tried to Upgrade to Windows 10 then there is a high possibility that $Windows.~BT in Windows 8 and Windows 7 is present. These files are not downloaded instantly as it takes time to download all the files which are present in $Windows.~BT folder. If you have installed any updates on your computer then they might be the result of this folder.
This folder is mainly present in the C drive of computer. $Windows.~BT is just a folder which you can see in any drive of your computer.
