I am having the same problem with no solution thus far.
I have read this thread fully & followed the instructions about using regedit to unregister those 2 .dll files. Restarted computer 2x and still cannot delete this file. It is currently 5.8 gb (in the BitTorrent Sync folder --- NOT RESILIO).
Can someone plz help me delete this file as it is unusually large and with my SSD only 128gb, it is taking up way too much space.
Those 2 .dll files, as listed in the registry, are : ShellExtensionOverlay64_128.dll & ShellExtensionOverlay64_17A.dll