Greg, I've tried the link, it appears that the extension has been installed. Will continue to use it to see how it helps.
Though I'm always conscious about the sites I visited, but sometimes I will accidentally touch sites which AVG reports that they are phishing or malware pages. That's why I hope to have adequate protection on my computer and browser to avoid any possible accidents for virus attack.
Will start the removal of 3rd party antivirus program and then attempt for Repair Install of Windows.