People have experienced problems in the past from cod4 multiplayer on the vista/win7 operating system due to the onboard sound cards.
Normally when my cod4 got this black screen it would crash showing me this error "iw3mp.exe has stopped working". Are you getting that error?
Is your onboard sound RealTek(TM)?
1. If so, then you will need to go into your control panel and open RealTek(TM).
2. You then need to click on the folder icon in the top right hand corner and click "disable front panel jack detection"
If your not running RealTek(TM) on board sound, just try plugging some headphones into the microphone jack in the back of your pc.
This is what helped me. BOL





