Hello Annie,
I have used AVG with good results. You can load it for free at
http://www.download.com/AVG-Anti-Vir...ml?tag=lst-0-2
It is pretty slick, and doesn't "hog" your system resources like others I have tried, such as Norton and McAfee, Norton was the worst as far as resource hogging in my opinion. And if you have to try to get rid of Norton and re-install it, good luck! Its a major PITA...
I do use McAfee now since i get the whole package as a free benefit from
Comcast, and it seems to work just fine, no problems yet.
AVG has daily updates that load automatically, sometimes more than once a day, telling me they must be keeping up on things.
Peace
Rags