I believe the celery has no math coprocessor. Change to an AMD or P4 and your FR will improve.
Gaming is akin to owning a boat. Once you buy one you find out its a big whole in the water you keep throwing money into. It's fun to own but can get costly. When I first got into an online WW2 dogfighting sim a buddy said I needed to plan on staying up with technology. He was right and I regularly upgrade my box about every 2 1/2 years. Here's how I normally do it just to keep costs to a minimum.
For instance, Frys Electronics, located on the west coast (there's one in Las Vegas also) has sales at least 3X a week. They sell MB/CPU combos for around $100-125 that use AMD or P4 CPu's. Now these are not the high cost/high end combos but will do an excellent job for a fraction of the cost. The last one I looked at one of thier ads they had a P4 2.6 Ghz CPU married to an AGP MB for $119.00. In a nutshell all ya gotta do is yank the stuff outa yer old box and plug in the new MB/CPU combo. All the MB drivers come with it and everything but your video card is on board. 5-1, 6-1 on board sound, they have on board video but its not really for gaming. You also have to buy some new faster ram which can set you back another $100 or so for 1GB.
Im running a cheapy motherboard with a 3.4 Ghz P4 and an X800 pro ATI card. Its rock steady at 75FR while using vert sync. If I turn of the vert sync I get 200 or so but you get 1/2 frames. I also have all the sliders to the left. I dropped an old geforce2 agp video card into it as a test and averaged 53 FR with the video sliders centered. Thats what I'd call brute CPU output! BTW, the 2.6 Ghz CPU using an ATI 9800 pro card averaged 65 FR with the sliders centered. Not to bad and absolutely flyable.
Alternatively you can buy a MB/CPU combo with the newer PCIE video cards. I think the video card manufacturers fell all over themselves trying to get the new cards to the market and, as such, some of the higher end agp cards are still equal to or better than alot of the new PCIE cards. Again spend lots and you get a good PCIE card.
I also found if you wait and buy a high end video card about 6-9 months after they come out you can usually pick one up for 1/2 price. This allows to you upgrade one step below the top sellers for a fraction of the cost.
IMHO the 3 main ingredents for solid FR's this game are CPU, Video Card and Ram. But you see for a a few hundred bucks you can upgrade every 2-3 years and be able to move forward with the games as they get better.
I threw out a lot of information just to give you some ideas of all the choices you have out there.
Hope this helps.