Windows XP running Cygwin/X
Oh, now I'm really curious. Are you a software developer stuck between (Windows / *nix) worlds? I have some experience with using Cygwin for building / using a cross compiler for a primitive OS kernel.
I used to do software development but that's a good while back now.
I've only got this netbook available at the moment and kept the XP that was on it for playing but feel most at home in a Unix-like environment. More so with the limited screen estate on these things where a text interface IMO is more flexible and I can control everything with the keyboard. Attached is what it looks like with a few clients visible.