Mark says that Norton anti virus on Windows 8 allowed a web search toolbar (called SearchUS.com) to get on Internet Explorer and it's been a pain in the neck to get rid of. Leo says that while it did happen, it's not really Microsoft's fault. They control 95% of the market and that makes it a huge target. Since it could have come with something else he installed, Mark may have accidentally installed it. Viruses can't get installed unless the user runs some sort of program to trigger them. Just having data can't really do it. It may be a security flaw in IE 10 that allowed it, though.
Jennifer updated her subscription to Avast and now her computer is all screwed up and they want her to pay for a certified technician. So, she went to Eset and they helped her by giving her an uninstall tool. Now she can't install Nod32 because it can't connect to the Internet. Leo says that is likely something left over from Avast that is causing the issue. Check out Avast.com's Uninstall Utility.