I had the same exact issue. (iw3mp.exe has stopped working)

This only happened to me after I re-installed Vista Premium, played many hours prior to the re-install.

My problem was definately related to my sound.

After reading through some of these posts, it kind of rung a bell, I always play with my Logitech USB Headset, but after doing the re-install of Vista, I disconnected the headset while I was working on getting the system back up and running.

As soon as I got all the drivers installed and all of the Microsoft critical udates, I installed cod4.

Failed to run, giving the error 'iw3mp.exe has stopped working' untill I connected my USB headet!

Now it plays fine, not sure what type, but my audio is integrated into the mobo, there must be an issue there, driver or otherwise, with the headset connected, the error doesn't occur.