Firstly .. get Sophos or Norton on all the machines, have them auto updating. Ideally run a server and have it passout the updates to the clients (we do updates every 2 hours).
If they can’t afford that, run Anti vir (http://www.free-av.com/) best bit of free kit there is, again have it auto updating.
Don’t click stupid emails from people you’ve never met talking about bank or password security, home loans, horny housewives, etc.
Lower activeX security settings to ALWAYS alert you. Ideally slap on XP service pack 2, move servers to 2003.
Make sure windows update auto-updates and installs new patches.
And that’s all you need. Do that and you won’t have problems with viruses. Schedule a regulary scan (should be weekly, do it overnight), I usually do a full scan once a month.
Never had a virus, had one once on a Mac, least with a PC it is relatively easy to clean and remove a virus… like everything else, move it to a Mac and it becomes a neigh impossible task the likes of which even Hercules would go “errr, hang on, I think that might be a little beyond me”.
