Desktop Composition Engine
The Desktop Composition Engine (or DCE) is a theme rendering engine used in early builds of Windows Longhorn. It is synchronized with WinFS, Avalon, and other internal Windows databases, as well as providing visual effects.
It is present starting with build 3683, but in a buggy state that only renders windows transparency. From build 3706 through build 4001, a new twirling effect when minimizing or closing windows is added. On build 4011 and build 4015 (main), DCE only provides transparency effects. Build 4015 (Lab06 n) and build 4018 were known to have additional DCE effects, including graphical animations and flapping windows while dragging. It is required in order to enable the Windows Aero borders on build 4039 and build 4042 (while build 4032 and build 4033 also have these borders, they have a bug in the DCE which causes it to use CPU processing instead of hardware processing).