Windows Longhorn build 4081

Windows Longhorn build 4081 is a Milestone 7 build of Windows Longhorn. On 23 January 2020, this build was listed in a BetaArchive thread by UX.Unleaked blog founder Grabberslasher to be released to the aforementioned site's FTP server. This build was released on 27 January 2020 in the fourth set of his 33 Longhorn/Vista builds along with build 5098.

Changes

 * This build is very similar to 4074, but it is the earliest available componentized build of Longhorn, meaning many core features from previous builds have been removed and introduced several bugs. These features were scheduled to be added in subsequent versions of the operating system, leaving what remains the bare minimum to run the system.

Installation
As typical for componentized builds, it tends to take a long time to install and can be unstable.

No mouse driver in WinPE
On some computers and virtualizers, the WinPE doesn't support the mouse, so you must use the keyboard to navigate the WinPE. This seems to be related to using a PS/2 mouse, as USB mice seems to work fine for the setup.

Upgrade
Attempting to upgrade from other builds is not possible as one of two outcomes may occur:
 * 1) A bugcheck with error code 0x7E after the second reboot. This is commonly observed when trying to upgrade from non-componentized builds, such as 4074 (via a registry tweak that reports it as a componentized build).
 * 2) An error during the file copy phase.

WordPad
WordPad does not start, as it will display with  instead.

Outlook Express
Outlook Express does not start due to registry errors and certain dependencies on WinFS.

Themes

 * The Windows Classic theme will not function due to a broken  file.

Explorer

 * CD and DVD drives behave like local disks.
 * Help and Support crashes Explorer.
 * Explorer will crash after adding the display tile in sidebar and won't launch again. A workaround is to create a new account via cmd.

Control Panel

 * Hardware and Devices folder does not open.
 * By default, sounds Control Panel applet is missing. It is possible to port  from another build to the   directory in order to get the control panel applet to work.
 * Task Scheduler from Control Panel shows a nameless folder and generic folder icon.
 * By default, the Phone and Modem Options Control Panel applet name is empty.
 * Computer Management displays script errors due to missing registry entries.
 * Device Manager has a bug that drivers can't be updated due to the Hardware Wizard Control Panel applet is missing. You can install drivers by using  utility from the Windows XP Driver Development Kit (DDK), or copy the   from another build to the   directory in order to get the updating drivers via Device Manager to work.

Creating folders
The option to create folders by right-clicking and selecting New doesn't work as the Folder entry is missing. Apply the following registry key to fix this problem:

DirectX
Although the Desktop Window Manager is present and can be activated by pressing Ctrl + Shift + F9 as in Windows Server 2008 build 4066, it will result in a black screen and close due to a broken DirectX installation. It can fixed via the instructions listed on the Windows Aero page.

Graphics
Enable VGA Mode after installing video drivers or the system will result in a blue screen of death with an error code of.

Windows Product Activation
Windows Product Activation is missing.

Safe mode
The Safe mode is completely broken and results in a bugcheck with code 0x7B. This is because the  key, located in    is largely incomplete and missing a lot of entries. Restoring the key from a build with working safe mode enables this build to boot in safe mode, but the display is not initialized properly which leads to no video output (which is seen as a black screen).