Windows Longhorn Build 4011 -

Byline: Retro tech correspondent Date: April 17, 2026

The sidebar is present—a vertical, resizable pane on the right side of the screen that hosts "tiles." These tiles are live, interactive: a clock, a slide show, a search pane. In later builds, these would become Windows Sidebar Gadgets. In 4011, they crash if you breathe on them wrong. One of the most beloved (and hilarious) features of 4011 is the Display Properties control panel. Microsoft engineers apparently decided to use this panel as a testing ground for every UI concept imaginable. windows longhorn build 4011

If you ask a long-time collector, “What’s the most fascinating bad build?” many will point to 4011. It is the digital equivalent of a concept car with flat tires: breathtaking in ambition, but undrivable on real roads. To understand 4011, you need to set the clock to early 2003. Windows XP was a polished success, but Microsoft was already looking beyond the desktop. The Longhorn project aimed for a "data-centric" OS where files, folders, and even applications were stored in a relational database (WinFS). The UI would be driven by a new graphics engine called Avalon, and everything would run on top of a new .NET kernel. Byline: Retro tech correspondent Date: April 17, 2026

Because for a few fragile minutes, you’re not using an operating system. You’re using a . Have you run Longhorn build 4011? Share your crash stories in the comments below. One of the most beloved (and hilarious) features