Excellent free antivirus software for my system!!

AVG's fine. It's actually still one of the best free virus checkers, I believe, and is really only beaten by the paid ones. As for tracking cookies, that's a separate matter. They're not a "virus" as such - they're considered "malware" (of which viruses are a subset but are usually considered separate... oh, so confusing). Something like Malwarebytes' free anti-malware scanner would get rid of them, though cleaning out your cookies regularly with something like Ccleaner would also work. You could also check your browser settings and tell it to refuse cookies (though some sites might not work properly if you do that).