No security program have 100% detection, if they did the virus problem on the net would be gone

Actually Avast missed the deadly snake that took over my computer but AVG, god only knows where I got that
Never install two AV programs as this will create all kind of windows errors and false positive detections

Or is this the AVG you have ? ( fake AVG )

Remove AVG Antivirus 2011 (Uninstall Guide)
http://www.bleepingcomputer.com/virus-removal/remove-avg-antivirus-2011