Resolved Network connection problems

We are experiencing frustrating problems of being able to set up a network between our 2 Windows 7 PCs. They used to talk to each other but somehow something has changed and I am stuck!

We have 2 PCs wired as follows:-
Main Pc is wired to broadband router (no Wireless connection)
Laptop PC wired to LAN socket on router using long cable to another room (We do not like wireless so have the laptop wireless switched off in order to rely on the wired connection).
Both are able to access the internet ok.

When I go to the Network tab on the main pc both pcs are shown and I can access the laptop ok.

On the laptop however I am unable to see the main pc at all.

I automatically back up various files on the main pc to the laptop using GoodSync and that is working but clearly won't the other way round.

What I need to be able to do is add the main pc to the "Network and Sharing centre" on the laptop and also the printer which is only attached to the main pc?

I have never used or set up the Homegroup option as I don't know what to do with that at all! Sorry if this sounds complicated but I have reached the stage where I am unable to think of anything else to do.