I've used Windows 3.1 and some other OS that I was too young to know what it is (probably something based off DOS or something). The earliest OS I've had on my own computer is Windows 95.
Commodore BASIC And DOS 4 (About 9,although DOS isnt quite me time,my first PC Was ANCIENT). Not too bad actually. I Had DOS Setup to automatically run a shell for me and it wasnt too bad.