Windows Neptune build 5111

Windows Neptune build 5111.1 is a Milestone 2 build of Windows Neptune. As of 2019, it is the only leaked build of Windows Neptune. It's also known as "Microsoft Neptune Developer Release", however much of the branding (including winver) still says "Windows 2000". The reported build string is also "5.00.5111" in some places. It was sent to developers on 1999-12-27.

This build cannot be upgraded from an earlier build, just be installed as a clean install. It includes Activity Centers, a new login interface, and changes to Help and Support and certain Control Panel programs. It's set to hibernate by default.

Multiple different copies
Most copies available online have been modified to not require a product key, have no timebomb, and replace "Windows 2000" strings during first stage of setup with "Neptune". The copy currently on BetaArchive was made from the original warez leak from 2000-01 and doesn't feature any of these modifications.