If you want your PC for networking by means of Hub or Router and it very simple you don’t need to plan to purchase a router if you are not connecting more than two computer on different network the cable or DSL routers have inbuilt switches to connect your computer to the internet connection .
Check whether all your devices like network card is being configured and then connect to the Hub or Switch and check all the computer are in workgroup and enter the IP address from DHCP device it means DSL router and if you don’t have DHCP device then you can enter it as 192.168.1.5 for the computer and the other as 192.168.1.6 and as on. To share files and folders you have to confirm whether sharing is being enabled and only few can access them.