Windows Longhorn build 4001

6.0.4001.main.021204-1515
	Build of Windows Longhorn
OS family	Windows NT
Version number	6.0
Build number	4001
Architecture	x86
Build lab	main
Compiled on	2002-12-04
Expiration date
Timebomb	2003-11-30 (+361 days)
SKUs
	Professional
Product key
	CKY24-Q8QRH-X3KMR-C6BCY-T847Y
About dialog

Windows Longhorn build 4001 is the first currently available Milestone 4 build of Windows Longhorn. This build was first discovered from screenshots that were shown by Dr. Nicholas Rush at YouArePwned's "Yet Another Longhorn Board", and by user bashar2000 on the BetaArchive forums.^[1] It was eventually uploaded to the aforementioned website on 15 January 2013.^[2]

While some features such as the Desktop Compositing Engine and Start Page are mostly retained from build 3718, it notably contains a new image-based setup procedure.

The build number jumped to 4000 to distinguish it from Windows Server 2003 builds, which had moved from the main branch to the dnsrv branch, meaning that the final build lab had transitioned from Windows Server 2003 work to Longhorn work. As such, this is the first known main branch build of Longhorn.

New features and changes[edit | edit source]

WIM installation[edit | edit source]

This build is among one of the first builds to use the new WIM-based setup routine, one of the first radical departures from the previous Windows NT codebase. The WIM-based setup routine works by having all of the setup files stored within a single WIM disk image, INSTALL.WIM. When the installation media is booted directly, the system boots into a WinPE (Windows Preinstallation Environment) and loads Setup. After it images the WIM file to the system partition, the system reboots to finish the setup by installing the user's hardware and then running the OOBE. Microsoft stated that their goal with this routine was to allow installations of Windows to finish in as little as 15 minutes.^[3]

While the installation is basic (using the Avalon interface) and lacks partitioning, it is capable of detecting hardware (including the CPU). As a result, it cannot be installed on processors older than a Pentium III, alongside a few virtual CPUs like the default emulated QEMU processor. The processor requirement would be removed in all subsequent pre-reset builds for unknown reasons.

As the ability to upgrade from a previous build was not implemented at this time, the user can only clean install this build.

Boot[edit | edit source]

The boot menu entry is now labeled as "Windows Longhorn" instead of "Windows XP Professional".

Out-of-box experience[edit | edit source]

A new OOBE was introduced, intended to replace the Windows XP OOBE used in previous builds. The OOBE in this build asks the user for account names to create and then finishes.

Sidebar[edit | edit source]

The sidebar is no longer transparent by default.

Windows Explorer[edit | edit source]

Unlike build 3713 and 3718, the user can now browse thru system disks and folders, as the "These files are hidden." message is not present.

Control Panel[edit | edit source]

The Control Panel is now in Classic View by default, however with no option to switch back to Category View.

Bugs and quirks[edit | edit source]

Installation[edit | edit source]

Some machines and emulators do not support this build, resulting in a crash or Avalon error in the WinPE part of setup.
The WinPE part of Setup can crash on real hardware if a USB drive is inserted.
Despite not being compiled in evaluation mode, this build can be installed on the current date.
As this build's setup cannot partition the drive, the drive must be partitioned before installation via diskpart.
Due to the setup not asking for the user's username, organization and time zone, the default username of "Windows User" without an organization is used in place. Alongside, the time zone defaults to the Pacific Time Zone.
The installer does not delete the "Windows PE" boot menu entry.

General[edit | edit source]

The "Low Risk" and "High Risk" text overlaps in the Windows Trust Manager.
The new taskbar cannot be right clicked.
The sidebar will fail to render properly when adjusting the resolution.

WinFS[edit | edit source]

The Windows Future Storage service does not function.

Media Center[edit | edit source]

It is not possible to install the Windows Media Center, as the required components are not present on the installation media.

Control Panel[edit | edit source]

Display Properties mentions the Luna theme as the Plex theme.

MyTVApp[edit | edit source]

MyTVApp cannot be opened, due to a crash in AvalonBrowserInteropProxy.exe.

Desktop Compositing Engine[edit | edit source]

When Desktop Composition Engine is enabled, it renders the graphics on the hardware layer, while the software layer is rendered as black or leftover data, which means that attempting to use software capturing methods (such as Print Screen) will not produce the screen correctly. Most hypervisors only renders the software layer, usually resulting in a black screen upon starting DCE.