my take on things...
im using a pirated copy of winxp with service pack 2. i have been using this exact same copy for seven (7) years now, and the only times i have ever been infected by anything was due to my own stupidity...
"ooooo she has nude screensavers? lets see this!!"
common sense and safer internet surfing habits go a very long way towards keeping a computer compromise-free.
use a java / flash / adblocker of some kind, and avoid russian porn and warez sites like they were SARS carriers. dont just open any old email attachment, and dont just plug in any old USB storage device unless you absolutely trust the owner of said device. dont share any files at all unless you know the person you are sharing with personally, or if said file is something you know for a fact cant be a carrier of malware. dont use IE and in most cases Firefox, as activeX is a vector for problems.
im starting to rant, so im gonna go now.