If you are doing a single still picture, just don't run the simulation.

To stop hair moving completely try using the following settings :-
"Bend Resistance" 1.0
"Position Force" 1.0
"Root Stiffness" 1.0
"Root Stiffness Falloff" 0.0

on each hair group you want to lock in place.
"Position Force" alone might be enough, so you might want to experiment a little to see what value combination gives the effect your looking for.