Windows Longhorn build 4015 (Lab06 n)

Windows Longhorn build 4015 (Lab06_n) is an unleaked Milestone 5 build of Windows Longhorn. This build was shown at WinHEC 2003 to demonstrate the new Desktop Compositing Engine which produces fancy graphical effects without relying on the CPU and slowing down the system. It is a GUI/end-user interface test build, as it is from the  branch. The same system that was shown at WinHEC 2003 was later used during PDC 2003 alongside a system running build 4018. A screenshot of this build is also known to exist, extracted from a Microsoft presentation about the Avalon graphics stack (TW04036_WINHEC2004).