I have two related problems. First, Google is my default search entry in IE9 but every search entry shows up in the address field as a "...search.yahoo.com" address. And the results page is plastered with Yahoo ads. I don't know what I have done to deserve this, there are no Yahoo entries in Control Panel / Programs and Features, and no Yahoo in IE9 / Tools / Settings. Full system scan by McAfee turns up nothing.
Second problem (now solved) is that my latest update of Adobe Flash concealed an installation of Google Chrome. That one at least I have finally eliminated. But meanwhile every HTG screen I open urges me to install Adobe Flash Player (again)... Leaves me feeling like a character in a vampire movie, at the point when they are turning up everywhere.