ViEmu is a cool add-in that brings vi/vim editing modes to several Windows apps, including Visual Studio, Word, and Outlook. It seems to have a lot of features that vi users are used to, and George V. Reilly (originator of the Win32 version of Vim, and currently releasing Win64 versions) has kind words for it:
All in all, I’m favorably impressed with ViEmu. It provides much of the muscle memory experience of Vim inside of Visual Studio. Technically, it can’t have been easy to impose such a radically different input model on VS or to emulate Vim and Ex fairly faithfully.
(ViEmu has 30-day trial versions available) – Link.