Since 2000 or so I've been using Norton for all my antivirus needs. Recently, however I've found it turning into an elderly prima donna: bloated and slow, demanding of attention, insistent on getting its own way and calling everything else to a halt whenever it deigns to perform.
With my yearly subscription about to expire, I decided I really didn't want to pay any more for the privilege of its company, so I've just been installing the splendidly-named Avast!, a freeware anti-virus application recommended me by friends (thanks chaps).
So far Avast! has been a lot more friendly (I'm running a scan while typing this, which would have been quite excruciating with Norton), though the siren noise it makes when it finds something amiss is a little terrifying.
It's also taken me all bloody afternoon to get it working properly, primarily because Norton simply refuses to work with these amateurs, and deliberately hangs around outstaying its welcome, perhaps in the hope of flowers from the audience. Gah. I think I've got rid of it all now, but it's been a grade-A pain.
And I'm particularly glad I've done it, as I now see from that Wikipedia article that Norton 2007 is completely incompatible with ZoneAlarm, which I'm also using. Bastards.