Try run as admin
reinstall cod4
"clean up" your pc.
btw iw3sp.exe is SINGLEPLAYER iw3mp.exe is MULTIPLAYER
IF YOU HAV ANY QUESTIONS OR I MAY HELP YOU MORE IF THIS DOESNT WORK PM ME
i dont need to clean PC coz i put win7 on yesterday so its got nothing except Msn,vb2010,combatarms,cod4 thats it.. im just re-installing it now!! ill get back to you if it works
and i dont play iw3mp.exe (multi-player) its shit!! lol
single player is better!