Back in the days when Windows Vista was still known by its codename, Longhorn, one of the flagship features being touted by Microsoft was WinFS.
This was the next-generation filing system to replace the robust but ageing NTFS. WinFS uses a relational database, supposedly allowing "users to uniformly organise, share, and manage all their data consistently, no matter whether they use different applications, online or offline".
Originally intended to ship with Vista, it was subsequently slated to ship at some point post-release. That didn't happen either. The latest version available to developers was released back in June 2006.
But while it appears to be completely dead, both Steve Ballmer and Bill Gates have said there are still plans to integrate it - or something very like it - into future operating system and application releases.
Vista Ultimate Extras This must rank as one of the biggest Windows flops ever. In an attempt to convince Windows customers to shell out for the most expensive version of Vista, Microsoft promised to provide a regular supply of additional content to Ultimate buyers post-release.
Over two years since Vista's appearance, Ultimate Extras consists of two games, a couple of DreamScene packs and some extra sound themes. Needless to say, there's no sign of Ultimate Extras in Windows 7.
Vista SideShow Vista SideShow was a sound idea. Attach auxiliary screens to things such as laptops and remote controls, and allow them to communicate with Vista to show information such as unread email and media playlists.
In practice, extra laptop screens needed the laptop to be powered up, rendering them useless. SideShow remote controls are a better idea, but they've failed to materialise, probably due to cost.