i find avast spot on (and free)
No antivirus can stop today's malware on it's own. They are simply changing too fast. For complete protection you need something like Comodo Internet Security which is totally free. http://www.comodo.com/home/internet-security/free-internet-security.php
I use Avira.
My norton had 1 day left so i have just un installed it and downloaded ms security essentials, norton slowed the laptop down so bad.
Hopefully ms will be better
I use both of these, works a treat. Been using them on Vista for 2 years now (Same install) and had no issues! (Also no BSOD, wahey)
I use linux.