What you hear in XP Media Center edition

I play games online and we use a program called Teamspeak and Ventrillo to
communicate with each other. On my system, when I push the key to talk, what
I am hearing in the headphones comes over the microphone. There should be a
way to turn off "what I hear" in the sound config. I am using Micrsoft XP
Media Center for the operating system, I believe it is the 2002 edition. Any
help with this problem would be appreciated. As it is I have to mute the game
whenever I want to say something to someone..
--
Reality is just an escape from your imagination..