CPU is a P4 3.06.hopefully not a choke point:hmm:

I have a PIV 3.2. On AS 16x and AA 4x, I'm getting 75 FPS on the bridge and 35 FPS when there's explosions anywhere. I have a hunch that something is wrong with your monitor max refresh rate and/or. At this point in time, expirimenting with various high refresh rates and v-sync might be your best bet.

Also, make sure that you use ctrl+F8 to view your in-game FPS to see how high/low it is.