Windows Longhorn build 4051

Windows Longhorn build 4051 is a Milestone 7 build of the Microsoft Windows "Longhorn" operating system and the build given to attendees of Microsoft's Professional Developers Conference 2003 in Los Angeles, California, which was held during the 27th to 30 October of that year.

This build comes in x86, x64 and IA-64 variants. The x64 version is not overly different from the x86 version, but it has a new setup style and several apps including Internet Explorer 6 have been optimized for x64 (often, the x86 versions do not run).

The Checked/Debug version was previously known to be not working in hypervisors; it will simply refuse to load setup due to a bugged processor check. However, BetaArchive user WindowsNeptune later found a fix to run the x64 version. It is also noted that this version does work fine on a physical system with AMD processors that contains the 64-bit AMD64 instruction set.

This build was compiled in evaluation mode, and can be installed on the current date, but once the timebomb is triggered, Windows won't let you access the desktop.

Setup
Although setup overall is similar to previous builds of Longhorn, you cannot upgrade to this build from a previous build of Longhorn, due to this being a PDC build.

winver.exe banner

 * A new winver banner has been added.

Explorer

 * New Documents and Photos and Videos libraries.
 * The prefix "My" was dropped in most of the remaining folders, resulting in new names for locations Computer, Network Places and Contacts.

Buddy matchmaker
This build of Longhorn includes an early version of Buddy Matchmaker, labeled as "Play A Game With Friends".

Internet Explorer
Internet Explorer 6.05 included an add-on manager, a download manager, pop-up blocker, and a tool to quickly delete browsing history.

Other new features and changes

 * A new TCP/IP stack. IPv6 is also enabled by default in this new stack.
 * Self-Healing NTFS was added in this build.
 * The top buttons in the migration wizard now function.

Do note that the x64 version of this build lacks the Sidebar.

Notifications
Notifications tend to re-appear quite a lot, until you reach a certain point where they'll finally close for real upon closing. To fix this, disable the Sidebar or click on Options, and then click on "Don't show this again".

TCP/IP stack
The TCP/IP stack has a few bugs, however, most of them were fixed in build 4053.