Windows Longhorn build 4074

Windows Longhorn build 4074 is the official WinHEC 2004 preview build, which was leaked in 2004-05. This build is a Milestone 7 build of Longhorn and the most famous build of Longhorn as it was distributed publicly. This build comes in multiple architectures, being x86, x64, and IA-64.

This build is the first to default with the Segoe UI font that would be used by default in later Windows operating systems. Many icons from Windows XP were replaced with new, high-resolution versions, as with build 4066. While the Slate theme is still present, it also contains the new Jade theme that is also present in build 4066. The default wallpaper has also been changed to "Leaves". The Jade theme also enables native Aero transparency, which has not been seen since build 4042 (however, full transparency will require you to put on the Desktop Window Manager and have the window small; if the window is maximized, then it will be opaque).

Features
Many features that were present in earlier builds have been removed or hidden in this build. As a result, the features that remained were improved: Do note most of the features related to the Desktop Window Manager such as Aero and Aurora only work on the x86 version. The x64 version lacks most of the DWM features, including the sidebar.
 * This build, unlike many other leaked builds, is the first build to have complete Aero effects in Explorer and Internet Explorer from the Desktop Window Manager. However, a registry modification is required to extend the effect into the full UI of Explorer and Internet Explorer. The green translucent effect is used natively in this build instead of transparent "Glass". Further modification (such as a modified version of the build such as TWIWMTB (Longhorn The Way It Was Meant To Be) or a patched  file) is required to replace the translucent borders with glass. On how to enable Aero transparency, go here.
 * This build also contains Aero Stars, an animated desktop which shows stars bouncing around the screen. It is somewhat buggy, and some graphic adapters may have trouble rendering it.
 * This build has the preview and filter panes improved, especially the Preview Pane, which is more functional than its leaked server counterpart, build 4066.
 * This build contains an Animated Preview Pane Aurora, but requires some modification to enable it.
 * MSN Messenger has been updated to version 6.1, with a completely new interface.
 * This build contains numerous updates to general prompts, ranging from the Autorun prompts to "not responding" dialogs.
 * A new driver installation system is implemented. As a result, most drivers that worked on Windows XP will often have the driver installation fallback to a "pre-release mechanism" upon installation.

Bugs and quirks

 * This build cannot be upgraded from a previous build, and can only be clean installed.

No mouse driver in WinPE
On some computers and emulators, the mouse does not work in the WinPE for this build and subsequent builds. If the mouse doesn't work, you must use the keyboard to navigate the WinPE. This seems to be related to using a PS/2 mouse, as USB mouse seems to work fine for the setup.

Creating folders
The option to create folders by right-clicking and selecting New doesn't work as the Folder entry is hidden. However, several unofficial patches have been created to address this issue. Also, folder creation may be enabled by applying the following registry key: Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\.Folder]

@="Folder"

Memory leak
As with most later Longhorn builds, this build's Explorer tends to leak memory after a while. Turning off the Sidebar reduces the effect of the memory leak.

Faulty file browse UI
The main File Browse UI has two noticeable bugs. The first being that the Navigation Bar only allows for navigation by clicking on parent directories in the bar. The second being that the Filter and Preview panes may occasionally appear black or show parts of content behind the window.

Safe mode
This build has a glitch with the Explorer Safe Mode desktop prompt. The prompt will appear titled "Desktop" and will ask to proceed to work in safe mode or to System Recovery. Clicking either button will hardly perform any action and will bring up another exact prompt. The desktop will not appear with the prompt and Explorer may not launch. This makes any work in Safe Mode almost impossible. Using Safe Mode with Command Prompt will work as long the Explorer shell isn't loaded.