Quick question:
How can one setup this firewall (Comodo) software to allow File Sharing in Windows XP?
You need to make your local network a trusted zone.
First look up your IP address and subnet mask. In Windows go to Start → Run → cmd → enter → ipconfig → enter → now lookup your IP address and subnet mask.
Second create a zone in My Network Zones (Firewall → Common Tasks). Choose Add → A New Network Zone → fill in a name like My local network → Apply. Now select My Local Network Zone → Add → A new address → choose An IP Address Mask → fill in your local IP something like 192.168.1.x usually and your subnet mask; usually 255.255.255.0 → Apply. Now check and see the new network defined. Exit using Apply.
Now we are going to use the Stealth Ports Wizard to make your local network a trusted network (Firewall → Common Tasks):
Choose “Define a new trusted network and stealth my ports to EVERYONE else” → Next → choose “I would like to trust an existing My Network Zone” → choose your local network zone from the drop down box at the bottom → Finish.
Now check your Global Rules and see your network added.