Once this is done, check your Windows directory for a directory named $WINDOWS.~BT. The icon may be translucent, since the folder is normally hidden, so check carefully.

KB3035583 is described by Microsoft as installing “the Get Windows 10 app, which helps users understand their Windows 10 upgrade options and device readiness.” It can be uninstalled by navigating to Windows Update from within the Control Panel, choosing “Programs and Features,” and then selecting the “View Installed Updates” option. Remove this update and then delete the folder, and you’ll reclaim your lost disk space.