Remote sound Raspberry Pi and Windows

I'm looking for creating a external sound reader based on raspberry pi.

I explain myself : I have a raspberry pi linked to speakers. When I read a music or video, I would like to have listen to my speakers through the raspberry pi.

I don't know how to start ot design such a app. I could use nodejs with node-webkit or qt to send the sound to a external device.

So, do you have an idea how to send sound to remote (through LAN) device ? and, on the external device, how can I do to separate data (only sound) and send it to speakers ?

Thank you.