I've used a lot:

Windows 3.1, 95, 98, 98SE, 2000, ME, XP, & Vista.

Mac, some older versions, and recent ones as well, can't remember exactly which version it was...

Linux: Knoppix, Slax, DSL, Puppy, UBuntu, & GoblinX, as well as some other ones which I can't recall at the moment.

How about you?

That's quit a lot.
As far as I can remember:
Something before 3.11 (black screen, green letters)
Then 3.11, Windows 98 ( & SE), windows 2000, windows XP
Ubuntu, Fedora Core, Debian, Knoppix.

Also used Vista for a few minutes to configure a wireless network, but haven't done anything else with it.
Never used a Mac though.
That's still on my wishlist ;)

I've used all Windows 95, 98, 98SE, 2000, ME, and now using XP Professional Eddition.

I have used a Mac before, as I used to work in an Internet Cafe, and they used only Mac's.

Windows 3.1, 95, 98, 2000, ME and XP.

Also Mac OSX and some linux distros, can't remember which ones though.

Windows 98, 2000, XP

All the windows except 2000 and ME. Haven't owned a Mac yet but definitely going to buy one at some point!

I have one win xp :angel:and solaris 10 :twisted:on the other machine