XP mainly. My "server" is Debian. I liked Redhat early on (like pre-2.0) but it became too much bloatware; too much "shield the user from editing a config file" crap. I even had a copy of Redhat 4.0 for DEC Alpha (anyone remember the cheap AlphaStations you could get and run WinNT and Linux on?). Oh, and the memories of Yggdrasil and Slackware are bliss.