IE randomly opens - brand new computer?

I got a new Toshiba Satellite C660 laptop this afternoon. One of the first things I did with my new computer is install Google Chrome, so that is the only thing ie has been used for. I also changed google chrome to my default browser. But now every 20 minutes or so IE just opens up ninemsn for no apparent reason. At first I thought there must be some default keyboard shortcut that automatically opens IE, but since it opened after I had not even touched the computer for a few minutes it seems to be just opening by itself. Surely it can't be a virus, so far I've only been on Google, Yahoo, Facebook, youtube, eBay, The local newspaper site, and my Uni's site, all of which are reasonably secure sites. I've had this computer for only 6 hours, it's unlikely it already has malware on it. Any suggestions to stop IE doing this?