Outlook 2007 renders e-mails with Microsoft Word rather than with Internet Explorer - you try using Spy++ to inspect the window class of the reading pane. While for Outlook 2003 it is Internet Explorer_Server, the new version has a _WwG class there.
Not only that, if you select a picture in the reading pane it shows the Word handles - you can even try to rotate it:

Not sure if Word is more secure than Internet Explorer 7 though :)