Operating System Beta, etc. Wiki
Windows Longhorn
6.0.4002.Lab06 N(ntvbl06).030108-1926
Architecture x86
SKUs Professional
BIOS date 2003-01-08 (compiled)
Timebomb 2004-01-06 (+363 days)
About dialog 4002-winver.png
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Windows Longhorn Build 4002 is one of the first Milestone 4 Builds of the Microsoft Windows Longhorn operating system. This build makes use of the Desktop Composition Engine seen in earlier Milestone 3 builds.

Unlike later Milestone 4 builds, Build 4002 uses the old i386-based setup routine instead of the newer one based on the WIM installation format. This is the first Milestone 4 build to use the new background unlike build 4001, which still uses the old M3 background.

Grabberslasher first gave the details of this build on his UX.Unleaked blog. On 2020-01-23, this build was listed on a BetaArchive thread by the aforementioned user to be released to its FTP, and was released on 2020-01-31, alongside build 4040 and build 5356.[1] WinUnleaked also had images of this build.

This build is specific in that it was built as a private build, with binary files having the VS_FF_PRIVATEBUILD flag set in their version information and the builder user name being present in the build tag, although the user name suggests that the build was built by the official Lab06 user account.

New features and changes

  • The new taskbar has been updated slightly, included a new clock on the taskbar, and a slightly lighter shade.
  • The sidebar has also been updated slightly, including the newer shade and slightly modified tiles.
4001-4002 DocumentaryWithSidebar.png
  • A new wallpaper has been added, making this build the first Milestone 4 build to use a new wallpaper (unlike Build 4001, which still uses the old M3 background).
  • MyTVApp has been removed.


  • WcmRegister.exe will throw out user registration errors upon login.
  • If restarting explorer while an application is still open, closing the app will still have its taskbar task shown.


This build cannot be installed via a CD boot because it attempts to incorrectly load the coverage.dll file. As a result, the system will BSOD after formatting the drive due to loading this file. setup.exe also attempts to load this file and quits due to it, but running winnt32.exe can allow setup to load.

During GUI setup, there will be a copy error that it fails to copy WinFSSyn.sql, WinFSSyC.sql, and WinFSSyM.sql, the user can safely skip copying these files.

Alternatively, you can use previous build (such as 3713) for these file to bypass this.


Ux Unleaked