Microsoft has confirmed in their
IE blog that users will be silently updated to the latest version of their IE browser to improve security.
Windows XP users will be upgraded to Internet Explorer 8 and Windows Vista & 7 users will be upgraded to Internet Explorer 9.
Users can opt out on this silent update by turning automatic updates off, but I recommend that you should always upgrade to the latest version as it adds new features and fixes bugs and you'll always be supported.