Fixed the iw3mp problem on my computer.
1. RIGHT clicked on COD4 Multi icon on DESKTOP.
2. Opened FILE location.
3.LOCATED iw3mp file and DELETED it and sent it to the Recycle bin.
4. PUT the ORIGINAL COD 4 DISK in my COMPUTER and CLICKED ON MULTIPLAYER.
5.Clicked on Recycle bin and restored iw3mp file backed to my computer.
Repaired my iw3mp files ...PROBLEM SOLVED......