i played doom 3 using the fps guide in the upper right hand corner and i am confused. when the game first starts, it is between the 50-70 fps range, but it cycles between these numbers very fast. also, when i open doors or enemies pop out, the fps can drop to <10 fps. here are my specs. amd 2400+ xp, 512 mb ram pc2700, and x800 pro 256mb card. help me. also, i have not oc'd anything because i don't know how. thanks!