IPv6 has been included in Windows since Windows XP - SP1. In Windows Vista, IPv6 is enabled by default. Even though the protocol is self-configuring, Windows Vista provides many tools using the UI and command line shell to configure the protocol. Here is a good recent link to "Configuring IPv6 with Windows Vista".

http://www.microsoft.com/technet/community/columns/cableguy/cg0506.mspx