Open any module in Design view (Or press Ctrl + G).
On the Tools menu, click References.
Click to clear the check box for the type library or object library
marked as "Missing:."
An alternative to removing the reference is to restore the referenced
file to the path specified in the References dialog box. If the
referenced file is in a new location, clear the "Missing:" reference
and create a new reference to the file in its new folder.
See Microsoft KnowledgeBase articles:
283115 'ACC2002: References That You Must Set When You Work with Microsoft
Or for Access 97:
175484 'References to Set When Working With Microsoft Access' for
the correct ones needed,
160870 'VBA Functions Break in Database with Missing References' for
how to reset a missing one.