Check out Moka5 (Score 3, Interesting)

The system you described is what I use every day. It is called Moka5 BareMetal, and you boot into it and select what virtual environment you want to run. The virtual environments (what they call "LivePCs") automatically update when the version on the server is updated. It keeps the user data (documents, settings, etc.) separate so you can revert and update the system without losing your data. You can suspend them and they start up pretty quickly. Makes using XP and Vista a lot more pleasant, plus I have a bunch of other Linux distros installed. It's a very cool system.

To stay on topic, there is a Moka5 LivePC for HaikuOS available for download, so you can try out Haiku without installing it.