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. This build was leaked on 2003-10-20.

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.

Features

 * 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.
 * Internet Explorer 6.05 included an add-on manager, a download manager, pop-up blocker, and a tool to quickly delete browsing history.
 * Only the basic sidebar tiles are included: Classic Tray, Clock, Quick Launch, Slide Show and Sync.
 * A new TCP/IP stack. IPv6 is also enabled by default in this new stack.

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

Bugs and quirks

 * This build cannot be upgraded from a previous build, and can only be clean installed.
 * Notifications doesn't work for unknown reasons.
 * The TCP/IP stack has a few bugs, however, most of them were fixed in build 4053.