Yesterday I played with CoLinux on my laptop with Vista x32. Tried it first with Windows 7 x64 but turns out that CoLinux is only available for x32 bit environments. Anyway, it started find with Vista x32 and I even upgraded the original image (Ubuntu 8.04) in two steps to 8.10 and then to 9.4. Had to increase image size from 1.7GB to 8GB. Increasing image size involves creating a new empty image file under windows, then mounting it under CoLinux and copying all information to it, quitting CoLinux and restarting with new image file. Instructions are in the Colinux FAQ section. Maybe 8GB is an overkill, and 4GB would have been enough, but I made it bigger just in case I will want to install more programs.
It works great, faster than virtual machine. Internet works, but I still have to figure out how to see local network.