Still i am using Pc security advsior which seem to be good going you can try this antivirus sofwtare http://www.bestantivirusreviewed.com

Sophos has one that runs quietly, updates automatically, has real time protection...only thing is, to be able to understand what it is doing, you have to be able to read Klingon!!!

I've just read all the replies,some of the antivirus things I don't know,so no comment on them.

Norton I had"Once" and never again,it gladly let a virus through that destroyed my Computer,I was put onto AVG and downloaded the free version and let it do it's thing for a month or so,since then I bought the full version and couldn't be happier.

It all comes down to what YOU want and what you want in an anti virus.I will however say this much,with most anti viruses,you have to do a scan every now and again,since I got AVG,i've never had to do a scan,it informs me when it detects a threat and then it's up to you if you proceed with the site your on or not .
You've asked for opinions?,That's mine.