I liked windows 3.1 it was simple and It worked (kinda)

The worst Operating system IMO is either Windows ME (i have a box running ME and everytime I try to run a program it gives me an unknown error) or Plan9 cause it's a peice of S*** for now but I hope that it becomes better because I like the name lol

The Best would have to be DOS 6 because it has never givin me any errors or had to be rebooted (it's 9 years old) BSD is also one of the best IMO because it's well unix and unix rocks. Linux not much to say about it, it works better than windows. Windows 2000 is also a farily good operating system runs well doesnt kill your system resources.