Right, first off computer specs:

OS - Windows XP (32bit i think) SP2
CPU - AMD 2.21 ghz X2 4200+
RAM - 3 GB (2x Crucial and 1 Kingston)
Motherboard - Foxconn WinFast 6100M2MA-RS2H
GPU - xfx 9600 GT (latest drivers)

Secondly the problem: I get really low frame rates while playing Team Fortress 2.

This is how TF2 usually ends up for me:
Find server with 50~70 ping.
Spawn with 50-60 FPS.
Run into the battle, FPS drops to 10-15/20.

I have no idea why this happens. I tried putting TF2 on the lowest settings, nothing changes, still the same low FPS. Then I tried running TF2 on my old 7600 GT, lowest settings, no improvement (sounds redundant yes).

So after that it leads me to believe that its the CPU that's causing the low frame rate. Nothing else eats any CPU or RAM power while TF2 is running and even then TF2 takes most of the CPU/RAM.

I'll post some screens later, but for now thanks for any replies.