Windows 8 build 7850

Windows 8 build 7850 is a Milestone 1 build of Windows 8. It is currently the earliest leaked build of Windows 8. On 2011-04-12, this build was first leaked as an Enterprise SKU image, then only much later, in 2015-01, additional SKUs were leaked.

Being early in development, many areas still says Windows 7 and the kernel is still 6.1 (in a similar manner to XP builds 2202 and 2211, 8.1 build 9299 and 10 builds 9780 and 9785). The default background image of this build is a bluish gradient with a cyan tint at the lower right and a message at the top telling not to leak this build ("shhh... let's not leak our hard work").

Features
Note: Most new features must be unlocked via registry editing.
 * Explorer Ribbon UI (Icons are all circles)
 * Centered title bar text
 * Built-in PDF Reader (basic)
 * New/Modern Task Manager (partially broken)
 * Webcam Application (fullscreen)
 * Auto colorization of themes
 * ApplicationExplorer (for early start screen?)
 * Aero Lite (basic)
 * Early beta of IE9
 * System reset (sysreset.exe)
 * Portable workspace creator (pwcreator.exe)

PDF Reader
While there is a very early version of the built-in PDF Reader included, it is disabled by default. It can be enabled using the following registry script: Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Applets\Paint\Capabilities] "CLSID"="{D3E34B21-9D75-101A-8C3D-00AA001A1652}" and then running  with any PDF file as an argument (or without any argument to open a blank page). It is not required to disable Aero to run the PDF Reader.

Modern Windows Task Manager
A preliminary version of the Modern Windows Task Manager is included as well. To enable it, run the following registry script: Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\TaskUI] "TaskUIEnabled"=dword:00000001 and then open.

Ribbon UI
A Ribbon version of Windows Explorer is included as well. To enable it, use the following registry script: Windows Registry Editor Version 5.00 [HKEY_CLASSES_ROOT\CLSID\{4F12FF5D-D319-4A79-8380-9CC80384DC08}] "AppID"="{9198DA45-C7D5-4EFF-A726-78FC547DFF53}"

Webcam Capture Application
An early version of the webcam capture application is included as well. To enable it, run the following registry script: Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\GRE_Initialize] "RemoteFontBootCacheFlags"=dword:0000100f and then run.

Auto Colorization
Create a copy of a theme from, add   to the end of the   section and apply.

Bugs and quirks

 * Windows Classic and the High Contrast themes are broken.
 * Changing the date appears to freeze up the Explorer shell.
 * Using Desktop Gadgets significantly slows the OS down.

Aero
This build appears to have a slightly broken Windows Aero theme, with only the top portion of the window frame using the blur effect, leaving the side borders transparent.

Upgrading from Windows XP
Upgrading from Windows XP to this build is not longer supported. Trying to upgrade from this build to 8056 will throw an error saying that you cannot upgrade from Windows XP to Windows Developer Preview.