I can say that this is a problem not shared by everyone - I bought GalCiv2 ultimate just a week ago and has seen nothing of this, so taking a look at drivers / settings might be an idea, as Valiard suggests.
(I actually have a similar PC to what you report - 9600 GT graphic card, xi-fi soundblaster platinum, and windows XP.. although calling it a beast is a bit of an exaggeration.
. If you have the very newest Nvidia drivers, I've run into some problems with those, so you might want to backtrack to 190.63.