Microsoft Headsey won't work in MW2

[unozero]

so I have a MS wireless gaming reciever and today I bought a Xbox headset Windows Detects it and it works over Steam but once I'm in-game in MW2 No One seems to hear me and the game chat comes over my speakers instead of my ear piece. What am I doing wrong?

 

[Krynn72]

What am I doing wrong?

You're playing Modern Warfare 2. LOLOLOLOL

I have no idea.