I'm not the audio guru here... but from what i've seen about the medusa 5.1 headset is that it is a USB headset. Is yours?
I've got the X-fi fatal1ty FPS and a pair of Zalman Theater 6 headphones. Here is how I hook it up.
See the 3 plugs White is Front - Gray is rear - Black is sub
The Black goes in the far right, Gray goes next to it, white next to that, and my mic goes on the far left.
These headphones are fantastic and have a perfect surround sound field.
BF2 - the M95 sniper rifle sounds absolutely incredible.... It's the sharpest, chrisp SNAP you've ever hear.... Sometimes when I pull the trigger it actually makes me jump... lol