Ok m8, you will need to know the ip addy's of the pc's currently on your network, you will find this by right clicking on my network places, in here you will see tcp/ip at the bottom of the list, highlight and select properties, on this tab will be the ip addy setup by pc world i presume. Make a note of this addy (ie 192.168.0.1), the other information will be the same ie the subnet mask - always 255.255.255.0.
Ok having obtained this info you need to make sure all your pc have their ip addy running in steps, eg: 192.168.0.1 for pc 1(the one connected to the router), then 192.168.0.2 and so on.
What are you sharing m8 ie internet/ broadband ?? or just files/printers....??