Vesta,
Just my opinion here...but if the firewalls are already enabled and the connections are working fine, leave them that way..Although the router you are using may have it's own firewall which may protect you from "outside" intrusion attempts, if one of the computers "inside" your network were to become infected with a "network aware" virus then it could easily infect all of the computers on your network unless protection is enabled...Keeping those enabled will provide protection against most network aware types of worms and viruses.
If you use "file sharing" on the network, you'll need to make sure that the "Exceptions" are allowed in the firewall settings. If you don't "need" file sharing between computers except in special situations, I recommend not allowing file sharing until you need it..
Hope this helps.
Grif
I use the Bellsouth Fast Access (2Wire) which has it's own firewall. It was suggested that I turn off the Windows XP Firewall which I did. My question is: I also have another desktop and a notebook networked with wireless adapters. Is it necessary to turn off the XP Firewall on these also, or does it really make any difference? Doesn't everything come through the main computer? Would it still create a conflict if I left the XP firewall on the two computers hooked up with the wireless adapters? Thanks

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic