Windows Neptune

Microsoft Neptune is an unreleased version of Windows. It was identified as NT 5.5, and was intended to be the first consumer version of Windows NT. However, it was scrapped, together with Odyssey (the planned successor to Neptune) and replaced with Whistler (Windows XP). As of 2017, only one build has leaked, but others may exist. Many major enhancements were planned for Neptune, including Activity Centers, which were HTML and JavaScript-based applications meant to replace Win32 apps. Early builds of Millennium (which was eventually released as Windows ME) usually contained files from Neptune; the purpose of these files was to help bridge the gap between NT and the 9x kernel.