Note: 

In order to compile OutCALL and OutlookAddin projects in Microsoft Visual Studio you will need the below listed files, which are distributed with Microsoft Outlook.

Depending of the version of Outlook, these files can be located at:

Outlook 2000:
C:\Program Files\Common Files\Microsoft Shared\Office10\mso.dll
C:\Program Files\Microsoft Office\Office\MSOUTL9.OLB

Outlook 2003:
C:\Program Files\Common Files\Microsoft Shared\Office11\mso.dll
C:\Program Files\Microsoft Office\Office11\MSOUTL.OLB