My first system was an Adam 8088 then an Adam 8086, then C64 then C128, then Apple II c, and e, then IBM x286 , x386, then Intel x486 SX, LX, DX, DX2, DX4, Pentium I, I version 2, Pent II, III, IV, IV x2 (over 1 Ghz version), Pentium Duo, Intel Core 2, and currently Intel i7.
Yep.. I go all the way back to cassette tapes and plug in cartridges and even card reader in some cases.
Hmm let's see I am 35 years old now and I have been messing with computers since I was 4 years old.. god.. way too much I have forgotten over the years that many this day and age will never know.
as for OS's.. DOS MS dos and Dr Dos and several other DoS programs / versions, OS2 Warp Gold, windows 3.1, Windows 95 , 98, me, 2K, XP, 2K5, 2K8, Vista, and now Windows 7. probably many in there I forgot to list.. but then again it has been quite a while.