yer well just share files at the mo but maybe all sorted as one pc can ping the other 3 but not one so i cheaked the internet cable and replaced it going to cheak now
I am presuming that you have checked workgroup names. Also have you tried plugging the non working router into a confirmed working port, just to make sure.
Setup the local unrestricted zone for the firewalls on all the pc's using a IP subnet, providing you have fixed IP's that is.
That should let everything on the subnet have full access and in theory disable the firewalls for all internal traffic without disabling them from stopping external traffic.
I didn't get the original question and couldn't makeout loads of words or any logical train of english
Also what OS are you running, what firewalls, what are u doing?, what services do you want to use (windows file+print sharing etc?)