From my own personal experiences I've found Norton and Mc Affee to severely slow down my PC's and cause all sorts of other issues too.
TrendMicro PCillin is probably the best of the commercial products. Of the freebies, I think AVG does a great job. Couple this with Comodo (firewall) and Lavasoft's Adaware - you've got yourself a pretty good line of defence without having your resources bogged down.
I've never done a defrag - but I'm sure to do one soon as it'll improve preformance.
Regarding Firefox - I've never suffered so much in the way of slowdowns, connection problems and viral infection as when I used this software. Once I'd gotten rid of this bit of junk and re-installed IE 7, my system was up and running again as normal.
Considering I've installed over a hundred programs/applications, have 80Gb boot HD crammed to 75Gb, plus around 400Gb of data storage on tap - it boots up pretty swiftly (30-40 seconds).
Compared to my accelerated A1200 with 814mB HD 'crammed' with a dozen apps/programs/games (ooh - about 20Mb's worth) - my PC's boot time is cr4p. Oh how I hate Microsoft products and PC's in general! :crazy:
