This is a mini Tos-link cable not a 3.5mm plug. Yes you would get Dolby 5.1 through it if you have a way of getting 5.1 out of your laptop. Most laptops don't have digital out though they have stereo 3.5mm headphones sockets.
What I've used in the past is something like this connected straight to a phono cable. Make sure you keep your levels low though, as said above though all you get out of the laptop is a stereo signal.