Built a decent gaming computer and have fps problems

So I spent roughly 360 bucks on this:

Card: ATI X1950 GT
Processor: Intel Pentium 4 3.0 GHZ
RAM: 2 GIG DDR2
Power Supply: 430 W
Motherboard: 945P IL9 Pro

When I play Team Fortress 2 there are times when my fps goes down to 12. It seems unplayable because of how choppy it can get. I don't understand it either. I play Call of Duty 4 with almost all high settings and that is perfectly smooth for me. I also play Counter-Strike Source and very rarely if there is enough action in one area it will drop down to about that low as well. It is really annoying. The recommended settings for Team Fortress 2 are:

CPU: 2.4 GHz Processor
RAM: 512 MB
Graphics Card: DirectX 9 capable graphics card 256 MB

I obviously exceed all of those. I have tried tweaking with video settings, resolutions, updating drivers, and even that doesn't help. However, the thing is I shouldn't have to do that. When I am indoors and it's a closed area my fps will be on average of about 40. When I'm outside with lots of people shooting all over the place is when it gets down to the teens and gets really annoying. My only guess is that it's because I have Pentium 4. Is that why?

Any help is greatly appreciated.

So how come they have recommended settings 2.4Ghz. Are they implying duo?

Yes.

The game was released on October 2007. 2.4GHz at that time meant E6600 or X2 4800+. I don't have benchmarks for TF2 but look at these for Prey:

http://www23.tomshardware.com/cpu_ [...] &chart=425

Your 3 GHz Pentium 4 is around 46 fps there, while the E6600 and X2 4800+ are at 109 and 94.

seems odd that you're getting such low framerates. my fps in TF2 never goes low enough to seem choppy and i only have a P4 2.6, 1GB RAM and a geforce 7600GT, and all at 1680x1050 and all settings at high.

40-80fps
x2 6000+
2gb ram
7950gt
running at 1280x1024.