If I may add my 2 bob's worth ...
My employer provides me with
Trend Micro's PC Cillin 2003, which I've found to be excellent. I run that on my desktop.
The boss also gives me
Vet Antivirus which I use on my laptop because it seems to me it doesn't load up the lappy as much as PCCillin did.
For a software firewall I don't think you can go past
ZoneAlarm. That comes in a basic, free version where the firewall is fully functional but the prog has few bells and whistles. There are also Plus and Pro versions with extra features.
My experience with these progs has been excellent. (2 x P4 boxen, XP Home, DSL broadband always on)
AA