What is going on with my rig?

Just built a new rig consisting of: Intel D875PBZLK mobo, Intel 3.0ghz 800mhz FSB, 1gig Corsair XMS pc3200 memory, SB Audigy Gamer, and my old GEForce4 ti4200.Now, on my old rig (a P4 1.5ghz with 512MB ram and the same video card) I was getting frame rates no lower than 16 or 17, any aircraft anywhere with all slider maxed except the 3d clouds and low water effects. With my new rig I cant get any higher than 5 or 7fps if there is a single cloud in the virtual sky. What am I missing? I have turned off several of the unecessary processes by way of msconfig and the services tab, and have tried disabling hyperthreading in BIOS (no difference by the way). Why was my performace so much better with the the old rig? I was expecting much better performace from this set up. Keep in mind that this is the same video card. My other two main games (IL2 Forgtten Battles and Call of Duty) both run much better at identical or better graphics settings.