friend with a problem~ Firewall a solution?

[Michael]

hbfriends:  but i can get on line at home sometimes...just depends if theres 
an unsecure or secure cercuit available

She is running XP and has wireless.She has an hp pavillion laptop so we can 
put a Linux Firewall on it. Will this help? What do I need to do to get this 
to work? Which is the security linux? I could just put that on and then 
'allow' things.