Vitality of Firewalls

[robfir]

I was wondering about how useful firewalls actually are, and wheter i should shut mine down, my old pc (pre SP2 and its firewall) had no firewall, and never broke.

The concentration of hackers to computers must be very low, and my bog-standard computer must be no challenge for them. My fear is that my firewall may be protecting me from computers running programs that want to do evil things to my pc, in which case it is obviously vital.

What is my firewall actually trying to protect me from?
Will shutting it down make my LW more useful to the network by allowing more uploads?

I have friends who have shut down their firewalls, with no noticeable ill-effect, and the no.of blocked events i get daily, from LW, strikes me as ridiculous in terms of malicious attempts to get inside, it seems more likely that they are just mundane attempts to get my shared files.