Windows Longhorn build 4040

6.0.4040.Lab04_N.030828-1910
	Build of Windows Longhorn
OS family
Architecture	x86
Compiled	2003-08-28
Timebomb	2004-02-24 (+180 days)
Works in
About
SKUs
	Professional
Key
	TCP8W-T8PQJ-WWRRH-QH76C-99FBW

Windows Longhorn build 4040 is a Milestone 6 build of Windows Longhorn and is one of the last builds for that milestone. Grabberslasher first gave the details of this build on his UX.Unleaked blog. On 23 January 2020, this build was listed on a BetaArchive thread by the aforementioned user to be released to its FTP, and was released on 31 January 2020, alongside build 4002 and build 5356. This build is one of the last builds to include the Plex theme, together with the main compile of 4042.

Overall, this build has a very similar feature set to builds 4038 and 4039.

Setup[edit | edit source]

Although setup altogether is mostly similar to previous builds of Longhorn, the numeral and clock sprites now no longer contain a transparent background.

Setup
Enter product key
EULA
Drive partitioning
Enter computer name
Copying files
Hardware detection

Features[edit | edit source]

Much of the interface remains similar to that of build 4038 due to Lab04's use of older code, likely from the main lab builds. This can be seen in areas such as File Explorer, where the back, forward, favorite and My Computer icons are identical to build 4038.
Related to Lab04's use of older code, the service winux does not exist, which means theming cannot be easily enabled/disabled.

Bugs[edit | edit source]

Installation[edit | edit source]

Some copies of this build's installation media cannot be booted normally due to a call to a non-existent index in the INSTALL.WIM by SETUPLDR.BIN. To install this build in this case, either upgrade from a previous build or use a WinPE from a previous build.

Safe Mode[edit | edit source]

Safe Mode does not log you on due to the login process change in build 4032, as it will result in There are no more endpoints available from the endpoint mapper. This was later fixed in Windows Longhorn build 4042 (main).

Upgrade[edit | edit source]

It is currently not possible to upgrade to this build. After the second reboot, Windows will corrupt the registry and will fail to boot, causing the error Windows could not start because the following file is missing or corrupt: \WINDOWS\system32\config\SYSTEM when upgrading from most builds prior to this one.
When upgrading from build 4028 ~ build 4039, lsass.exe terminates with a critical error, and the system will become stuck in a bootloop. The only workaround is to reinstall Windows. This bug persists until build 4053.