If you are using McAfee, open VirusScan console and make sure all the categories in Unwanted Programs Policy are checked. I don't think they are by default. Larger AV companies get sued by those small malware... err... 'Potentially unwanted program' producing companies claiming their programs are legit. They can use exploits to drop the malware producing the popups trying to get you to buy a semi-legit product. By making you configure the 'unwanted programs policy', I guess the AV companies protect themselves from some lawsuits.