XP + Free
John Gotze is having the same XPerience as me, since I cleaned up my old WinXP partition to sync up my own User Experience with colleagues who are using Windows. (I find I can't empathize with clients and their problems as well when I'm running Linux and they're pulling out their hair, alone.)
It is what I was talking about 18 months ago in "The Power of Mozilla Firefox and OpenOffice on Windows" for Sys-Con. XP with all those free apps will get you through the night...it's alright...
Funny, I used to be about 2 years ahead; now I'm slightly less untimely.