Ok i have played single player without a single problem. All settings totally on max at 1920x1200 without even 1 slowdown... Everything runs completely smooth. The menu for singleplayer is fast and responsive as well. HOWEVER.. when i go to the multiplayer menu IT LAGS so badly. like mouse speed is lagy, button response is lagy. Then i joined a game and STILL lagy as ****...
ok i re installed the game a third time !! bloody hell and it was still laggy so i did so more research and found the **** reason why it lags... its actually a glitch they need to fix.... really **** up indeed. I checked off dual video cards and boom no more lag... WTF lol
here are my specs
Q6600 @ 3GHz
Asus Maximus Formula
2gb Corsair Dominator Ram
700 Watt OCZ PSU
2x WD 500GB hard drives
I used to have a problem with call of duty 4 too, it would play fine and then randomly freeze in game for no apparent reason. what solved the problem for me was exiting out of rivatuner and atitool. apparently, some other people were having the same problem and that worked for them too. i hope it works for you. it really pissed me off since cod4 is amazing but its just so frustrating to crash so much.
There was something similar in COD2. If you checked the "Dual Card" box or whatever, you would actually see a performance boost even if you just had a single card. Granted it was only a few FPS, but it could mean the difference between the M1 firing like a sub-gun or a bolt action.