I have used AVG, PC Tools brand, (forget the name), and several years worth of Norton.
My Norton 2009 is the cleanest running, lowest impact Norton I've seen in 10 years of
using their versions.
Strictly & Fwiw, PC Mag gives it rave reviews; see link below.
I want no part in a Norton Sucks debate, similar to Macs are the best, etc...
It is just my 2Cts from a very paranoid 'net user. And, imo, the AdAware Anniversary Edition is
very, very good for nailing adware/spyware. And, CC Cleaner for really cleaning out the crap...
GL,mD
The Best Security Suites for 2009 - Reviews by PC Magazine