Windows Longhorn build 4015 (main)

Windows Longhorn build 4015 (main)  is a Milestone 5 build of Windows Longhorn.

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.
 * Windows Explorer has been written in .NET managed code, although this often causes memory leaks and frequent crashes.
 * The new taskbar given from the Windows Sidebar is enabled by default. This new taskbar overrides any theme that is utilized.
 * 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, 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 has been updated. This replaces the bubble notifications with icons on the taskbar that was used in previous versions of Windows. These push notifications would be later introduced in Windows 8.
 * 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.

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.
 * Password hints have no effect on this build as the new login screen has no option to show a hint.

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.

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.