There's some good info to be found on google when you search for netBIOS.. The name implies what it does, BIOS for networking;
netBIOS "facts"turn off netBIOSTho; handle with care, if in doubt, don't follow these instructions and get a firewall.. There are plenty to choose from, even free ones (like mentioned ZoneAlarm is real good, as good as the ones you must pay for)...