Windows Longhorn build 4015 (main)

Windows Longhorn build 4015 (main)  is a Milestone 5 build of Windows Longhorn. This build was leaked on 28 April 2003 by WiNBETA.

Setup
Setup has received a few changes compared to build 4011. The product key section, however, makes all letters inputted uppercase and now also adds dashes per every 5 letters. Upon partitioning the disk, you will also be given a warning when proceeding to install Windows.

A new page of Setup has also been added - choosing the computer name. Usually, this is randomly generated, but you can change it to whatever you want.

New features and changes

 * The wallpaper has changed to a Milestone 5 background, being slightly darker than the Milestone 4 background and containing the Windows logo instead of the Longhorn logo.
 * The latter year in the Longhorn branding in "winver" and About Program dialogs has been changed back to 2003.
 * A new login screen is utilized, replacing the Windows XP login screen. It also uses the wallpaper found in builds 3706 to 4001, however it doesn't use animations found in later builds.
 * Windows Explorer has been written in .NET managed code, although this often causes memory leaks and frequent crashes.
 * Parental Controls is updated to now restrict games that are rated higher than a specfic ESRB rating.
 * This build includes Libraries. The libraries included is the Photo and Video Library, Music Library, Document Library, and Game Library; the latter doesn't work. It was later introduced in Windows 7.
 * WinFS now works, but it often causes memory leaks.
 * Notifications once again have been slightly updated.
 * The Desktop Composition Engine can be enabled with the  command in the Run dialog box. Note that a DX8 graphics card is required or DCE will crash. Only window transparency is included.
 * The Plex theme has received a few updates, such as buttons now having animations upon hovering over them.
 * The Windows start button has changed, being different than the start button shown from builds 3683 - 4011.

Sidebar and taskbar
The new taskbar given from the Windows Sidebar is enabled by default, and you can no longer get the old taskbar with the sidebar enabled. This new taskbar overrides any theme that is utilized. Tiles for the sidebar have also been updated slightly, such as the search tile, which has been modified to be slightly more fitting.

Bugs and quirks

 * The hardware setup tends to hang easily, after a while, you can press Shift+F10 to open the Command Prompt. Then, run  and terminate the process   to log in. Due to this, you will also not manage to reach the Out-of-Box Experience.
 * Password hints have no effect on this build as the new login screen has no option to show a hint.
 * Once copying files has completed, setup will fail to create a boot.ini file. Although booting will still be possible, NTLDR will default to C:\Windows.

Installation
Most copies of this build's CD are not bootable due to corruption, since it results in an "NTLDR is missing" error. If booting from the installation media only results in an "NTLDR is missing" error, it can only be upgraded from an earlier build (Except Build 4011, which will give a 0x6B BSOD). However, the current copy on BetaArchive doesn't have this error.

Memory leak
Windows Explorer has several memory leaks which can make this build difficult to use. Turning off the Sidebar will usually stop these memory leaks. WinFS is also known for causing memory leaks.