A couple of tidbits of info....
re; the Klez worm.... it might be beneficial to check with your isp as well. Mine offers email filtering, which I enable, but with only basic filtering turned on. This automatically virus checks each message and checks subject headers for known spam content, all BEFORE I download the mail. I get daily mail filter reports, notifying me of any message filtered out, the sender and subject, and the reason for the filtering. I can then visit the email managament site of my ISP to have any messages I want sent on to me delivered. Over the past 2 weeks, my ISP filtering has caught at least 10 or so Klez infected messages, with NONE getting through to me.
Also.... I run Norton Internet Security (antivirus, personal firewall, ad-blocking, and parental controls all available) and it has been intercepting repeated SubSeven Trojan attack attempts (not email attachments.... direct attacks on me simply while I am connected to the net, which I would never even know was happening), most originating from Korean ISPs.
Between these two methods of protection, I have intercepted MANY malicious attacks before they could cause any problems, and I would highly recommend using both.