To add to what's already been said:
Firstly - agee that this should be a sticky as a lot of users may not be aware of what's going on with their own PC
Secondly I refer (again) to this thread which I've referred to before - previously regarding PeerGuardian but has lots of good security tips: http://forums.overclockers.co.uk/showthrea...&threadid=82920
Thirdly - something like NIS is great if you're an average to intermediate PC/internet user like myself - though it may spoon-feed you at times and stop you doing what you want but once you understand what you're doing then you can progress onto more advanced settings and get to know what it all means (hope that makes sense!?)