COD4 Files Missing (PC)

Hey

I have just been playing on my mates pc on COD4, I joined a server which started to download mods (it was a rifles only server) which I didnt know or want to do, so I done a CTRl ALT DEL and ended task half way through it downloading these mods. Now when he clicks on the shortcut on the Desktop it says unable to find iwmp3.exe. Even when we clicked on the COD4 icon with the disc in My Computer and click on play multi-player nothing happens at all. He has now wiped the game off his p.c and has installed it again and it was half way through the intall when it said iwmp3.exe not found or something similiar, and does exactly the same thing as before, and will not let him play the game anymore.

please help

Dan