A. You need a full version of Internet Explorer installed with the ActiveDesktop
support to enable Preview.
You can verify if you are running the full version of IE by checking for the file ie4shl95.cab among IE setup files. If that file is present you are running a full version.
A. Office documents can be previewed only if they've been saved with
an embedded preview picture. (There's a specific checkbox in the File/Properties
dialog of Office applications that enables this.)