We've had some great feedback to the bulk email to members about protecting your computers while online. Thanks to everyone who took the trouble to reply.
Microsoft also offer Security Essentials for free - download from here:
[url="http://windows.microsoft.com/en-US/windows/products/security-essentials"]http://windows.micro...rity-essentials[/url]
I've personally had issues with AVG not detecting trojans and found Norton to be deeply invasive, so ended up going with Kaspersky in on my laptop, which is a great application. I use Clamwin on the desktop PC but maybe there are other alternatives out there too.
I'd be grateful if the mac owners could post their advice re: sophos and other apps they're aware of for mac as there was some great advice in some of the responses.