I get this problem of really low fps and freezes when ever i play call of duty 4 after i play another game, to solve the problem the only method i've found is to re-boot my pc and that seems to sort it all out, it just annoying after a while re-booting your pc every time u want to play call of duty 4
My graphics card is an Radeon X1950 Pro and all my temps seem to be fine
E6400 dual core
asus p5b-e motherboard
Did you update your drivers, install any new programs prior to your system acting up? Did it work correctly before at any point or has this been an issue from day 1?
This seems to be usually from a software conflict of some sort. I know it I have DVD343 running in the background and try to start Command and Conquer Generals my system would crash and I would get the blue screen of death. As long as I would shut down that program first it would never happen.
Just an idea but you have to start somewhere when you are troubleshooting...