I visited my parents at the weekend, and as always one of the things I did while there was to do some admin on the computer. Their virus software - CA's ezTrust - had expired (actually, I think the product had been canceled, after them giving it away free through a deal with Microsoft after the SP2 launch). I replaced it with Symantec's Norton Anti-Virus solution - partly because it was easiest, partly cheapest, and partly because it's a product I feel I can trust my parents to use effectively and that will protect their machine without too many potential problems. Personally, I don't use it, both my desktop machines and the servers doing email scanning use ClamAV.