A couple of computers make a couple of Windows versions:

On my 486DX: Win 3.11 and Win 95 SE in dualboot
On my Pentium 166MMX and my Pentium 233MMX: Win 98 SE
On my Athlon64 3000+: Win XP SP3
On my Athlon II 635: Win 7 Ultimate

And my next computer will probably be Windows 10 ;)