You ever want to edit that AutoComplete list that outlook uses (this is stored in [Your Profile]\Application Data\Microsoft\Outlook , and it always saved as the profile name of Outlook with .NK2 extension btw)

Then look no farther than the freeware http://www.nirsoft.net/utils/outlook_nk2_autocomplete.html

What about removing duplicate messages or contacts in outlook. Grab yourself a copy of http://www.vaita.com/ODIR.asp