Seems like we get this post every week now, maybe we need all the possible solutions in a sticky,1) Go into your miles folder inside your Activision folder, then change the mmssmp.asi file to mmssmp.bak 2) if you have just updated your sound drivers then roll them back 3) If not uninstall the game then update your sound drivers, then re-install game to new drivers 4) Plug headphone jack into mic slot, try one at a time, see if any work, if not just Google IW3MP.EXE and see what else it throws up, most fixes are usually the ones i gave you but different things work for different people, the one that always works for me is link 3) Reinstalling game to new drivers.