Doc Martin makes a number of errors when talking about his computer: the network doesn't recognise memory at all, the motherboard does; neither network cards nor memory ever came with jumper switches; and finally, doing anything like replacing memory or network cards with the computer switched on would, at best, not work. At worse it would fry the memory and possibly other circuitry, especially for computers of that vintage; and in all cases would require a reboot to see if the changes had worked.