Yep, you read the title right! Windows 8 Build 7850 (M1 Final) has been leaked and is now available for download from different torrent websites. The leak was first posted on BetaArchive private FTP site and it has been confirmed by several reputable sources that this is a legitimate build of Windows 8 which was compiled on 22nd September 2010.
The Build number of the leaked 6.1.7850.0.winmain_win8m1.100922-1508_x86fre_client-enterprise_en-us.iso is 6.1.7850.0.winmain_win8m1.100922-1508 and it is the final M1 and the last 6.1 build.
The first beta of Windows 8 is expected to drop this fall while the OEM availability is expected in the end of 2012. Folks at BetaArchive who posted the leaked build also posted some awesome screenshots of Windows 8 which you can find here.
Download Windows 8 Build 7850 Milestone 1
File Name: 6.1.7850.0.winmain_win8m1.100922-1508_x86fre_client-enterprise_en-us.iso
File Size: 2.45 GB (2,637,101,056 bytes)
Update#1: Install Windows 8 (7850 M1) on VMware Virtual Machine [How-To Guide]
Update#2: Install Windows 8 (7850 M1) From USB Flash Drive [How-To Guide]
Update#3: Create Window 8 Bootable DVD From ISO Image [How-To Guide]
Update#4: Create Window 8 Bootable USB/DVD with Windows 7 USB/DVD Tool [How-To]