Windows 8 build 7850

Windows 8 build 7850 is the official Milestone 1 build of Windows 8, which was originally uploaded to BetaArchive as an x86 Enterprise SKU version on 12 April 2011, then on 17 January 2015, an x64 version of this build was uploaded to the aforementioned website along with additional SKUs for both the x86 and x64 architectures and its server counterpart. It is the earliest available build of Windows 8 to have an x86 architecture.

Due to its earliness, many areas still say "Windows 7" and the kernel version is still 6.1 (much like builds 7700, 7746, 7777, 7779 and 7814).

Files from the ARM32 compile of this build were discovered on the Microsoft Symbol Server on 24 May 2022.

This is also the very last build to use the Windows 7 branding and to use the 6.1 kernel version as Windows 8 build 7875 uses the Microsoft Confidential watermark branding and the 6.2 kernel. However, the setup screen still uses the Windows 7 branding until Windows 8 build 8045.

Internet Explorer
The new Internet Explorer 9 user interface is now enabled by default; there is no longer a need to patch the application in order to enable the new UI.

Redpill
This build's Metro is almost identical to the previous build. The Start screen has a yellow-orange background in debug compilations of this build instead of the white background seen in free compiles, the reason behind this is currently unknown, but it is possibly made to test the accent color.

Other features include:
 * Support for 32-bit UEFI boot
 * Support for booting from an exFAT partition
 * 4K Native logical sector boot
 * Hybrid boot

EULA Hash / Hash ID
has code to print the hash ID in the about box and desktop watermark, which appears to fail in this build (hash ID is only printed if the function to obtain it succeeded). The public symbols for this build give a mangled name for this function as, although compiler or link-time optimisations removed and inlined the second argument (length of output string buffer in characters). The function retrieves the default value in the registry key. This value must be REG_BINARY of size 128 bytes; this data is split into eight 16-byte buffers,  is equal to the nth byte of each of the buffers XORed together.

General

 * On some machines, it is not possible to install this build due to a  bugcheck.
 * Some graphics drivers may prevent the system from booting and will result in an  or a   bugcheck.

Installation

 * On some machines, it is not possible to upgrade to this build due to an error when booting into the OOBE.
 * The messages shown when the setup is starting or restarting the computer have the last word cut off.
 * The original upload of this build from 2011 is bundled with the Windows 7 RTM pre-installation environment.
 * Setup may hang when restarting after the hardware portion. Restarting the machine will fix the problem.

DWM and Aero

 * The Aero functionalities do not work on VMware Workstation versions 14.0 and above due to changes that are incompatible with the graphics stack.
 * 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.

Windows Explorer

 * Changing the date has a chance of crashing the Explorer shell.
 * Using Desktop Gadgets significantly slows the OS down.

Internet Explorer
Like build 7700 and build 7814, the Internet Explorer 9 Beta engine is unstable and may crash when accessing HTML5 websites.