|All PC's have to have the exact same workgroup name.|
If they already do, then check and see if they have the built-in windows firewall enabled and it they do, is it set to block everything? If it's blocking you have to set it to allow LAN traffic.
If it's not the workgroup name, and it's not the firewalls, then you need to create shares to connect to.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.