Neptune largely resembled
Windows 2000, but some new features were introduced. Neptune included a logon screen similar to that later used in
Windows XP. 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. The Activity Centers contained traces of
Windows Me, then code-named Millennium, of which it was originally developed for, but were broken due to
JavaScript errors, missing links and executables to the Game, Photo, and Music Centers. In response, some Windows enthusiasts have spent years fixing Activity Centers in build 5111 close to what Microsoft intended. User management was also improved in Neptune with the introduction of several new user types as well as a dedicated full-screen user interface. The new interfaces were primarily implemented using Internet Explorer's web technology, often using the then-new Mars framework. A key focus of the Neptune project was to experiment with user experiences that did not require manually saving previous work; some of this effort is visible in the only available build, which enables hibernation by default and requires the user to take extra steps to fully shut down the device. In early 2000, Microsoft merged the team working on Neptune with that developing
Odyssey, the successor to Windows 2000 for business customers. The combined team worked on a new project codenamed
Whistler, which was released at the end of 2001 as
Windows XP. In the meantime, Microsoft released Windows Me in 2000 as their final 9x series installment. Early development builds of Whistler feature an improved version of the
logon screen found in Neptune build 5111. == Triton ==