When you are in a LAN connected to the Internet behind a router with NAT and harware firewall, you don't need a software firewall in the computers.

A computer firewall in a computer in a LAN only brings trouble. You will access Internet but you won't access the LAN because the firewall is locking the multiple ports that the LANs protocols use.

The connection with a server will fail, and moreover you won't see the LAN at all.

Scenarios:

• The user installed a firewall (willing it or not). Not only disable the firewall but uninstall it. Keep it installed and disabled only if it a portable that goes out of the LAN and connects direct to the Internet in other circumstances. In this case the user can enable the firewall, but should remember to disable it when in the LAN.
• The Windows XP firewall is enabled. Unable it through the LAN Network Connection properties. The same considerations applies for portable users.