You did not need the network hdd, but now that you have it, let us understand what you want, and then let us understand what you should do.
You want to store all your music on your network drive, right?
So you can do that. Then you mount your shared drive as E: or something on your windows PC. Add this path to library of your squeezerbox server running on PC.
Similarly, you can mount the same path to your laptop and add to itunes library.
Problem with this is the amount of data trips that would happen on your network. Network drive to PC, PC to squeezebox. Unfortunately, for squeezebox to stream your music, it needs a squeezebox server, which means you need to switch your PC on when u want to listen to your music. AFAIK, it can't just play from a network location, even though it has a squeezebox server kind of stuff in-built.
Though there are some "network drives" that can run squeezebox server on them. This one doesn't seem to do that.