|Continuing along those lines:|
I do, highly recommend Avast (as I said above) and use it on quite a few machines, but to throw out another, I personally use Webroot Secure Anywhere on five machines at home. I have been using Webroot's software for many years through it's evolution and it has always been good, but this latest software is nearly invisible when in use. It does a great job, It is not noticeable, it does not bother you about constant updates, it uses system resources very sparingly, it tells you about a threat blocked in a =n intelligent way, and it only reminds you about renewing it annually (or 2 years if you prefer), unless you want to set it to automatically renew. Yes, you do have to pay for it, but they have a very nice discount for 3 or 5 machines. For me, it is worth it (5 machines is I believe a bit more than Norton charges for one machine, and 3 machines are even less than they charge for one, but that is also for much better protection, more intelligent use of resources, and less hassle).
You have to be a little bit crazy to keep you from going insane.