Sound Blocking

I'm wondering if there is some sort of software or option I'm missing to block sound coming out of your computer and playing in your microphone. For example when someone talks in skype it doesn't play through my microphone. Everyone complains they hear every sound from my games but they never hear themselves talk in skype. So there has to be the ability somewhere right? I'm using a Creative xfi titanium pro and want to get rid of the god awful thing I've heard good things about the meridian 2g if anyone has any suggestions. My main focus is gaming but I listen to pandora and other music frequently.