Thanks, and where to discuss mouse-keyboard configurations?   
Thanks very much for quick reply, I think I understand now.    
I am just now running the current 1.5 open beta on a not very powerful laptop and it is working fine.   
I am working on a configuration to fly with mouse and keyboard only, using PPJoy (Parallel Port Joystick). So far I have    
Mouse Axis X = Roll 
Mouse Axis Y = Pitch   
I  can toggle the 'Mouse-Joystick' with a keypress so mouse movements  don't steer the plane, but I haven't figured out how to get mouselook  working yet.    
Of course all this is a topic for another thread -- can anyone suggest where I should discuss this sort of thing?