Luc,
In Windows Mail, click on the 'Contacts' Icon in the menu bar.
Then click on 'New Contact' in that menu bar.
Actually I assume you have already been there and found no 'New Contact' in
the menu bar. That may be because the Folder Type has gotten messed up and
is no longer 'contacts'.
Having the Contacts folder open, click Organize, then properties. Customize
tab.
Under What kind of folder do you want select 'Contacts' from the drop down
list.
Now you will have the 'New Contact' button.
Michael