Hi R. Richards,
Tell your friend that av-scanning is only part of the story here. The other side of the medal is keeping your operational system updated and patched (yes for all of the proggies your run) and have a hunch of things you do online that can put you in serious trouble (taking risks and the wrong attitude). Some people do not realize that without a proper av-scanner and firewall installed they are likely to be infected within half an hour, and that is no exaggeration on my part, these are facts.
Windows out of the box, visiting certain sites without the proper protection and fully patched software, being open to malicious scripts, transversal redirects etc. can run your computer in the ground, and don't blame a malicious hacker, it can be just the rogue malware from the guys that have your "best" interest at heart, oh just click this pop-up or message. Bingo. And a lot of folks that venture out on the Internet have no more knowledge than "you can click right, and left, and if that does not help you just click it away". Sad world, really, and some earn big money keeping this this way,
polonus