Cod 4 not working

Hello,

My cod 4 game doesnt work for pc. When i boot the game up it says iw3mp.exe stopped working. It happens evrytime i load up Cod 4 multiplayer. Ive recently bought the game off steam but it has made no difference ive asked steam but have got no response. I think the problem happened when i started to uninstall it and half way through i stopped it.

Could you please help me fix Cod 4 cos i think its the greatest game ever!!!!

Cheers vamooosh