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#1630
First off, Ronaldo, although we're on the final version of Windows 10 with Build 10240, the $Windows BT folder is there as a matter of course and and although similar, has nothing to do with the upgrade from Windows 7 or 8.1. Within that folder you can drill down to the "Install.ESD" file that's used to create an ISO in order to do a clean install of Windows 10.
So, not to worry; it's there and doesn't eat much.
Unless you want and need to clean install Windows 10, I wouldn't worry about it.
Of course, I always do a clean install simply because an upgrade from one OS to another can (but not necessarily) bring along nasties that may be lurking in the old OS.