So, going back to the Antivirus software, I am currently using Avast. That was the first software that would work with Vista x64 that I have at home. After reading a review on 3dnews, I am thinking about giving a try to another antivirus software (that was actually almost hated in the computer lab during my college years for not being able to handle/scan the macros in the Word and Excel files but I think they had improved during the last years).
Anyways, if you are looking for a free antivirus solution for home, it might be a good choice. It's free for personal use, it is rather light and has a good reputation.