generally the COM components will be deployed in an app server (e.g. MTS - Microsoft Transaction Server). Once the COM component is deployed in MTS, u can instantiate it (e.g, in an ASP page) using Server.CreateObject("theComponentName")
and get a reference to the object.
Now considering the component as a black box, u can try executing the methods that are provided in the component.
Have a developer (microsoft platform) in ur company to better xplain u abt this.
*also search this forum on COM/DCOM testing. there are a lot of discussion on this i believe.