You're machine is definitely powerful enough to handle BC at it's highest settings but, to make things a bit smoother:
- Turn off Space Dust (this is an annoying feature anyways)
- Turn off Motion Blur (this is a cool effect but usually used for nice screen caps)
- Turn off Enhanced glows (also a neat feature but, more system intensive)
- Leave everything else on its current settings
Bare in mind that BC is not a multi-threaded game (too old) so it can't take advantage of the multiple cores in your Phenom. However, 3.2GHz is a fast base speed so, your machine still has some good horsepower to run the game pretty well.
Another thing is that your GTS 250 is an excellent card but PCI-E does not use system memory to supplement its on board memory like the older AGP standard did. So, it's a fast card but even though 1GB of video RAM is generally quite good... when you have high poly mods with high res textures (and several iterations of them) on screen, you're going to start chewing up that video RAM like crazy. What I have found to be the real "system killer" when it comes to playing BC are the quality of the textures. The higher the res on the textures, the more video RAM is taken up. The textures are loaded/stored on to video RAM and when you have a lot of high res textures (in the 2048 range or higher) I've seen even really beefy systems take a hit on performance.
My best recommendation is to sometimes use the "medium" res textures on some of the high res mods. The medium res on those mods usually have textures in the 1024 range and that's still quite good.
Bottom line, it's all about finding that right balance.