Comment If Netware/Win3.1 can do it, I'm sure Linux can :) (Score 1) 80
Our school used to have Dell 486/25's set up as diskless clients, running Netware 3 and Windows 3.1. You logged into Netware from DOS, then it automatically loaded windows. The machines wouldn't boot if the network was down.
This increased security no end, especially once they removed the floppy drives. Also PCs set up like this are less nickable.
Anyway, I'm sure the hardware exists to do it.