AVG6 Free works well on most systems. Light on resources, and has good
detection if you keep it updated, which is true of any AV. I am sure there
are lots of others here with varying opinions and they'll be happy to
promote their favorite programs.
However, the best AV protection you can get at any price is to practice Safe
Hex and use your common sense. First; read up on the various types of
viruses and what to watch for. Second; sedate your mouse so it don't get
click happy the minute messages hit your inbox. Third...in order...if it
sounds like a really great deal, it ain't. If you think the Date of the
Month went to all the trouble to find your e-mail address and is hot after
you, NOT!! And, if you think Billy G has told MS to send you a personal
message about protecting your security, he didn't. Heh...he has enough
trouble keeping up with MS's own security woes to worry about you and yours.
Fourth; don't rely only on an active AV, you should also have an on demand
program as a backup. I use F-Prot as my backup. But, there are others that
work well too.
Good luck!
Jan