As Mohamoss suggested, inherit your MainMenu from System's MainMenu.
Then add a method to it that creates menu items and subitems with the
strings passed to that method.
Define some properties like display value, form_to_open, a Dataset or
something that can store some data. Then retrieve the menu structure from an
XML file or from a database into the Dataset and foreach record, call the
method declared above.
Create a dll with this control.
Drop your control on a form and on the load method of the form, call the
method on your MainMenu control that retreives menu data and creates the menu.
I guess this is something you want to do.
Hope it helps.