McAffee and Avg both default to scanning only executables. You must go in and set the resident, complete scan and scheduled scan to "all files".
AVG is autoupdating and free, and I've never found a virus on any of my client machines IF they keep up with replacement versions when notified and IF we fix it to do all files. Just wish they'd fix the default to all files, but they won't respond to emails unsolicited for suggestions.
NAV is the simplest, autoupdating, high rate of success - It is my first love, but if there are problems with expired/renewal or switching between versions (eg. Norton Internet Security, Personal Firewall, Antivirus) and something goes wrong, I have spent HOURS HOURS trying to go through methods of removing, RNAV-RNIS etc and on the phone with NAV after reading all the online suggestions, removing directories manually, cleaning registry by hand and STILL fail to get it reinstalled.
So if I start having uninstall/reinstall issues, I have been turning to AVG with great relief.
McAffee has failed too many "IN THE WILD" awards for me to trust it. Norton's been passing those tests without fail since 1999. AVG is passing recently though it is not as "old" as NAV in longevity.