I have tested out a 'flavor' called Cooperative Linux. basically it lets you run Linux on your computer simultaneously with Windows without the need for an emulator. Essentially, its just a modified kernel.
It is a little time consuming to install. It isn't a real distro since it is only the kernel. So you'd have to do a net install of your favorite distro. Their website has directions for this for several distros including Debian, Fedora and Gentoo. Preinstalled images can be downloaded for testing.