This posting inspired me to find the solution for the same problem in Outlook 2003. I could not find an "XML Structures" box under the toolbar tab as was suggested in the first post for Office/Outlook 2007.

But in Outlook 2003, under Tools / Customize, choose the middle tab
"Commands", in the left menu Categories, choose "view", then in the right menu Commands, scroll down and find the button "Toggle XML Tab View", then drag this button out of the menu and drop up in your Outlook toolbar, then click it. Voila! The pink xml tags vanish.

Lee