Random Thoughts

Firewalls are extremely useful, particulary those that block outgoing, as well as incoming connections (ZoneAlarm, for example). To give you some idea as to why - say, for example, you have unwittingly downloaded a trojan that is logging your keystrokes and sending them back to a server on the internet. With a firewall monitoring outgoing access, even if the trojan works as it should, you would still have to give it your permission to report its findings back to base. Incoming firewalls block connections to any ports that may have been accidentally or maliciously opened on your computer.

Onto the subject of people attempting to gain control of once machine - it doesn't matter that you're not the pentagon. It doesn't matter if you have no personal information stored on it at all; the fact is, hackers make hundreds of thousands of pounds by forming what are known as 'botnets' of compromised 'zombie' machines, which are then commonly used in criminal enterprise, DDOS attacks, and so forth.

This are simple examples - there are many more. Firewalls can be a pain to configure, but they are well worth it - not having one is simply ridiculous.As for free antivirus - I would recommend Avira's AntiVir. AVG is good, but the daily scans on the free version can be a bit of a pain.