network sharing

Hi,

im hoping someone might be able to help me here.

im simply trying to get it so that all the computers computers around my house are allowed to have a nice friendly time together …
y’know … go online… see each others files etc.
but, no matter what i try … or what tutorials i read on here … i still get the same thing.
nothing.

the computer that has the modem is able to view the internet… and travel around just dandy …
but all the other computers that try connecting through this computer end up adrift and not allowed to join in on all the reindeer games.

oh … and no computer can see any other computer on the network … not even the main computer …

ive tried setting up the trusted network through the wizard … and that doesnt work.
ive tried to setup some rules etc as to what one tutorial had mentioned … and the other computers still were all alonely.

turn off the firewall and everythings back to normal and everyone can see everyone … everyone can go online etc … turn it back on … and nothing.

so, can someone please tell me what im meant to do? … cause im about one key stroke away from just killing all firewalls and letting the hackers do whatever they sodding well want with the computers.

well … at least someone should get to enjoy these things, right?

sanks.