I don't tend to use parrallel and Serial these days, but I would be stuck without them as I do occaisionally need them. As for PS/2, I would be very wary of buying a PC which didn't have them. Even though my mouse is USB, it has a PS/2 adaptor which i use. My keyboard is PS/2 and if I were to buy a keyboard in the future, that would probably also be PS/2.