I ave always been an AVG fan until I started having problems caused by the use of a Netgear backup system on my main machine when windoze (XP Pro) would crash quite often at the end of the boot sequence. I changed this machine over to Avast and had no problems. Since that time AVG has gone through numerous revisions and having installed it again with the Netgear utility on a new machine I have again had no problems. IMHO AVG and Avast are two of the free utilities worth considering.
P.P.