I am not sure you need a computer. When I mapped "this old house" I just made a sketch of each room and the outlets, then used a breaker finder to track down each one, verifying by turning them off one at a time. Two people make this go faster than one.
You start getting a feel for how things are wired so it gets easier as you go.
It is time consuming but once you get the map made, it is a great addition to your important papers.
