Windows Neptune

Neptune was the codename for a version of Microsoft Windows under development in 1999. Based on Windows 2000, it was originally intended to replace the Windows 9x series and was scheduled to be the first home consumer-oriented version of Windows built on Windows NT code. Internally, the project's name was capitalized as NepTune. Neptune largely resembled Windows 2000, but some new features were introduced. Neptune included a logon screen similar to that later used in Windows XP. A firewall new to Neptune was later integrated into Windows XP as the Windows Firewall. Neptune also experimented with a new HTML and Win32-based user interface originally intended for Windows Me, called Activity Centers, for task-centered operations. Only one alpha build of Neptune, 5111, was released to testers under a non-disclosure agreement, and later made its way to various beta collectors' sites and virtual museums after it was leaked in 2000. It is the only build of Neptune that made its way to the public. Other builds of Neptune are known to exist due to information in beta builds of Windows Me and Windows XP; a build 5111.6 burn lab disc was also shown during a Microsoft Channel 9 video in November 2015.