Windows Longhorn build 4086 (lab03 dev)

Windows Longhorn build 4086 (lab03_dev) is a Milestone 7 build of Windows Longhorn. On 23 January 2020, this build was listed on a thread by UX.Unleaked blog founder Grabberslasher to be released to the BetaArchive FTP, and was later released in the tenth set of his 33 Longhorn/Vista builds on 2 February 2020 with its other compiles.

Installation

 * As typical of builds in this build range, it tends to take a long time to install and can be unstable.


 * Partition and format a drive from a previous or later build prior to starting installation.
 * After the second stage of setup (hardware detection phase), the system will not restart automatically and get stuck on a blank screen with the desktop watermark. Simply reboot the machine to finish the setup.
 * This build can't be installed in VirtualBox since it will BSOD with an error code of  after rebooting from the second stage of setup. It is recommended to use another hypervisor/emulator instead, such as VMWare or QEMU.

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 does not function due to a broken  file.

Explorer

 * Windows Explorer is more prone to crashing than in previous builds, especially when shutting down Windows.
 * 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.
 * When the Aero taskbar and sidebar are enabled, the Taskbar erroneously uses the Sidebar background.

Control Panel

 * Hardware and Devices folder does not open.
 * By default, the Phone and Modem Options Control Panel applet name is empty.
 * Computer Management displays script errors due to missing registry entries.

Graphics
On some computers, you will need to enable VGA Mode after installing video drivers or the system will result in a blue screen of death with a error code.

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).