To start off and eliminate the obvious things...I have reinstalled drivers for all hardware, i've defragged, cleaned the computer up, etc. I dont run background programs while gaming, i've reinstalled COD4. I have also bought a new PSU, motherboard, CPU and RAM. None of these things have even BUDGED my issue. And at this point i'm pretty desperate for some good tips or information. Hope you can help.

To make it simple....my only problem is my FPS....it just stays in the 20's on average. In a more video demanding area of the map it drops below that; when i'm around nothing it might hit 35 FPS if i'm lucky. The only thing I have changed from the stock graphic settings are bullet impacts and blood. I have also changed the resolution to 1280x1024 due to a 19 inch monitor.


Specs
Motherboard=Biostar NF520-A2 AM2
CPU=AMD Athlon 64 X2 5000+ 2.6GHz
RAM=2x1024mb Corsair XMS DDR2 800 PC64000(2 gigs dual chan)
Video Card=ATI Radeon x1650 Pro 512mb PCI-E
PSU=Corsair HX 620-watt
OS=Windows XP
I do not overclock.

Given I just installed a new motherboard, could there be a BIOS setting issue? Its probably unlikely, it doesn't make sense to need to change BIOS settings before getting full performance on a motherboard.

All the upgrades you made won't have as much impact on performance as the GFX card. The 1650 is a relatively weak card(no offense)and is likely the bottleneck. You should save your loot and pick up either a 9600GT or an 8800GT... either of those cards will give you much higher framerates. If you can't swing either of those, an 8600GT would be a decent option that would give you much more playable fps.

i have a x1650pro 512mb, p4 3.0ghz oced to 3.6ghz with 720mhz Corsair ram.

i do 5-60fps @ 11xx*xxx resso.

Settings All off execpt bullet impact

Textures: Extra
High
High

The graphical settings on high just arent worth the FPS drop.

but I know I do 20-30 FPS when i put 1280*1024 with everything at high with max AA and AF and texture reso.