A comment on Slashdot pointed me to coLinux; sort of like User-mode Linux, but running on Windows instead. Very interesting. I just installed it and downloaded a Gentoo root filesystem image supposedly customised for coLinux. Since there are still many (more or less valid) reasons that I want to keep running Windows on my desktop machine, this looks very appealing. This way I won't have to wait for Windows ports of all the server software I want to run (Apache, Subversion...). I'll post again when I have something up and running.