Locked at 10 FPS

I have a Dell dimension 4500 S about 2 years old I think. (time flys too!) Also, 512 Mg. mem., Integraded Intel 3D AGP Graphics. 20GB Value Hard Drive, XP home. I see that I'm locked at 10 FPS and run about 9.8-9.9 in all modes except Spot view and then the frame rates run at about 6.5 or so. Also it could be my imagination but my frame rates seem to improve after my first flight. So I take a short flight around the hill and back before I get serious. I see and read some of you get 2 to 3 times better rates than I. Some planes are terrable for my frame rates such at the 747. For some reason smaller planes give me better rates. What do I need to to get up to speed with the rest of you guys and gals? ::) Thanks for any help.