Build 4001 showcased an early version of the DCE (the predecessor to the Desktop Window Manager or DWM). This engine allowed for advanced graphical effects, such as windows that twirl around the screen as they close.
The "Library" concept in Windows 7? Born in Build 4001's WinFS prototypes. The modern Settings app’s category-based navigation? A ghost of the Longhorn Panorama view. windows longhorn 4001
Microsoft began planning a major release codenamed "Longhorn" (named after a bar at the Whistler-Blackcomb ski resort). The goal was ambitious, to the point of delusion: a brand new file system (WinFS), a completely new graphics engine (Avalon), and a new way of handling web services (Indigo). Build 4001, compiled on February 19, 2003, and leaked shortly thereafter, represents the earliest public taste of that unhinged ambition before reality set in. Build 4001 showcased an early version of the