Windows NT 3.1 build 340

Windows NT 3.1 build 340.1 is the October 1992 pre-release build of Windows NT 3.1, available in both standard and server editions. The latter was leaked on 3 November 2017 by The Distractor on BetaArchive. It is the earliest leaked build of the server version of Windows NT, at the time still called "LAN Manager for Windows NT".

This build is often mislabeled either as build 319.1 or 328.1, which are actually file versions of its kernel files ( and  ). NTFS now works in this build.

Around the release of this build, the known error in the processor detection routine appeared, preventing installation on the Pentium II and later without modification, and it made its way into the final release, and it persisted into Windows NT 3.5. It was finally fixed around Windows NT 3.51 build 1002.1.