In the unlikely event of your router having only one network connection you could always use something like this:
Amazon.co.uk User Recommendation
Connect the router to the powerline adapter (in a mains socket) and then connect the disc and your PC to the second powerline adapter.
There's a whole suite of powerline adapters available - single or multiple ethernet connections/with or without mains pass-through. Different makes are also compatible with each other so, if you want to add more later, they don't need to be the same brand.