Remove items from Word 2007 "Save in" list?

I know how to add folders to the Word's "Save in" list that shows up as the left pane in the Save As dialog. I would like to further customize that list by removing items I never use but are placed there by default - e.g. Trusted Templates, My Recent Documents, My Computer, My Network Places. When I right click on any of these, the Remove option is grayed out. Is there a registry tweak or some other method for removing these from the Save in list?