I personally have all the above, except I use DMZ for gaming (server host) needs, and my computer hasn't seen a bit of malicious software yet (almost 18 months old).
Make sure other users on the computer (if any) are locked down... I left my sister and her friend on my laptop alone (her user account, admin) for a couple hours a week ago, and had to reinstall Firefox, CS:S, and a couple other things afterward. Strangely, only some files were missing, and they weren't uninstalled.