Windows 2000 network at the office.
At home, my main machine is a WinXP Home. Much to my joy, people have begun donating old machines left and right, so I've recently added a Win95 and Win98lite to my arsenal. I have a couple more machines I haven't done anything with -- one of them is going to run Redhat soon and I'm considering sticking BSD on the other one so I can learn about that. They're idle for now though, as I unfortunately have more machines than monitors to stick on them. :)
