Conservative! :p
Hm...
OS1.3 1991-1993 Then again I only played games on the old A500, so that doesn't really count.
OS3.0 1993-1998
OS3.1 1998-2000(?)
OS3.5 2000-2000 (?)
Win2k 2000-2003(?)
WinXP 2003-2005
Mac X august 2005-october 2005
and back to XP
-edit-
Actually, I also used OS3.5 somewhere too...when was that released? 2000?
