really poor frame rates in COD4 with Nvidia 8800gt

I have a Pentium D running at 3.00 GHz with 3 Gig of ram. It's a stock Dell XPS 400 except for the additional RAM (Corsair XMS) and the BFG 8800 GT 512 OC I added 6 months ago. When I play Call of Duty 4, in either single or multiplayer, my frame rates drop as low as 6 FPS! The best I can get is about 30, and that's in a very small space with nothing to draw. And it really doesn't matter which resolution I set it to, from 640x480 all the way up to 1600 x 1280 the frame rates don't change very much...they're always below 10 during the helo insertion in chapter two, and between 8 and 12 in multiplayer. And I read where everyone else with this same card gets 90 FPS all the time. I have tried everything I can think of, including:

- Changing all the graphics options. Even at 1024 x 768 the frame rates are around 8-10. With shadows off, smoke edges off, and AA at 2 it;s still 10 FPS.
- Reinstalling both Nvidia drivers and COD4.
- Opening a support issue with Activision (They're NOT helpful. After 5 or 6 communications with them I get questions like "is your computer running lots of other programs?" and "Have you got the latest drivers?" Sheesh.
- Opening a support issue with BFG, who simply referred me to Activision after a brief test to see if the card was running correctly.
- changing all sorts of settings in the Nvidia control Panel, I can't even begin to list everything I've tried...

Is there anyone out there who has a new idea? My system is not overclocked in any way, never has been. It runs Crysis pretty well at max settings, though I suspect my frame rates of 12-18 at max settings are lower than what I should see as well.

Thanks in advance.

sounds like a processor / power supply problem

Same build as my old PC, extactly, only with a 8800 instead of a 8600. At 1024/768, you should be able to run a high/medium mix at around 40 FPS most of the time, its not lack of decent hardware...

Might be lack of power, as posted above.?

that's weird i have a 8800gts 512 which is a bit faster than the 8800 but not alot maybe 10% and it runs cod4 maxed out at a constant 60-80fps.
Check drivers and stuff make sure you don't have many files open when playing make sure there is no virus scan going.

and !!! is there even a 6 pin for the 8800, on the "hell's dell's machine,plus the op changed/added to the ram,, corsair,which may not even like/be compatible speedwise the installed ram,non,.:> )

I agree with many of you, it sounds to me like it may be my power supply. TWhen I installed the 8800GT it said a minimum 500W power Supply was needed. The one that came with my dell is a 350, but I thought I'd give it a try. I didn't mention this before because I wanted to see what people would come up with on their own, and thanks to many of you who came up with the same conclusion I have now ordered a 650W Corsair with 52 amp capability. It should be here early next week. I will post the results here when I get it installed.

Thanks again to all who responded here!

turn off your vsync.