This is how you can show headers in Outlook 2007;
Click view > arrange by > custom > other settings in the reading pane section insure the Hide Header Information box is unchecked.
To see the complete header information of a particular message follow these instructions:
Open a message.
On the Message tab, in the Options group, click the Dialog Box Laucher .
In the Message Options dialog box, the headers appear in the Internet headers box.
Hope this helps. J.B.