In previous version to Word 2007, if you use Word as your email editor in Outlook and Outlook has been opened, Word stays in memory ready for Outlook. It will only close when both Word and Outlook are closed down.
At this point, all the temp files should close. However, if you have been doing any copy/pasting, the temp files created by copy/paste may remain until a reboot because they are still 'active' on the Office clipboard.
Regards: tf1