Sometimes even good behavior results in some nasty stuff. I try to avoid any and all links and I won't open email if I don't know who sent it to me. Even with that, some viruses attack people you know and send you email with malicious software. Heck, even here there have been several attacks............so from personal experience I will say be cautious but make sure I have some type of anti-virus software. Eventually, no matter how careful you are, it happens.
Great points and you are exactly right. Just as being perfect driver can result in an accident caused by someone else, safe computing behavior cannot guarantee that you will never be infected. However, those that only rely on security software to protect them without practicing safe behavior is the equivalent of driving 150mph and running every stop sign and red light simply because you are wearing a seat belt and have an airbag installed.
As for the malicious email from someone you know, this is a bit of social engineering by the hackers that has proven very effective for them. One thing to keep in mind if that the "From" field on an email is just like the return address on snail mail ((you can put anything you want in the field).
I'm using AVG Free and Superantispyware that Mike recommended. Love it! Have had no problems at all!
These are two products that I use and still recommenced. There are others that I like as well, but I encourage my customers to choose from the products that I use everyday. That way if someone calls with an issue, I am usually able to answer any questions within just a few minutes. Brief calls like this are free which saves my customers money and saves me time.