I am using D50 too, I suppose D50 allows you to change 3 different settings in P Mode(correct me if i am wrong because i seldom use P Mode), but I do not have an external flash so I have no idea how the external flash will restrict the settings in P Mode.
I suggest you look up the user manual for details. :bsmilie:
(1) When using P mode w/o external flash, your camera will give slow shutter speed and big aperture value e.g. 1/8sec , f3.5
(2) When using P mode with external flash, your camera will give a min. shutter speed (usually fixed at 1/60sec) and big aperture value e.g. 1/60sec , f3.5. The speedlite flash is intelligent to handle the exposure.