Norton is killing your PC, and need more resources and always and always sending messages, i think that Macaffe is tha same also...all these programs nedd more resources < HD,RAM,CPU
i recommend for you KasperSky, very silent and light antivirus
Nod32? I never heard that admin. How good is that antivirus? Can it wipe off the Brontok virus? I use AVG and Norton. So far, updated Norton can clean up Brontok latest version as last month but AVG cannot detect it.