McAfee

[Undertoad]

Linux

"Careful computing", although I wouldn't recommend it to everybody, it has worked perfectly for me. I have had no viruses or anything ever and I have never used anti-virus of any kind. This is where you:

a) never run anything from an untrusted source;
b) never INSTALL anything from an untrusted source;
c) use Firefox;
d) use Thunderbird or a web-based email such as Gmail;
... a+b+d) all executable attachments in email are untrusted;
e) if you must IM, use Pidgin;
f) don't go clicking on all kinds of shit everywhere.

People also advise that you

g) don't operate your system with Administrator rights

...although I do this all the time because I'm a bad-ass.