360 no sound with VGA and audio setup

[WatchTower]

So I bought a 360 today and the official VGA cable. I connected the VGA to my monitor and the audio cables to a phono adaptor tha that came with it and connected it to my PC speakers.

I can get a great picture but I'm getting no sound I've set the sound to stereo on the 360 and set my volume high on my speakers but I get nothing.

I need help.

 

[WatchTower]

I used a dual phono coupler and a pair of phono leads to hook my 360 up to some PC speakers with the VGA cable while I was sorting out my main setup.

That's what I'm doing but I'm getting no sound.

 

[WatchTower]

I'm using Logitech X-210 Speakers