We also look for any Outlook data files (*.pst)where the users save offline email (if they use Outlook, of course).

Take a look at the user's Local Settings \Temporary Internet Files for something they may have opened and didn't do a Save As to keep it.

Has anyone encountered a problem with saving SUBFOLDERS under the Outlook Address Book? I lost a subfolder called Personal (it didn't get exported like the root of the Address Book). Had to rebuild from memory (yeah, right!).