>I don't understand the question about "dependencies". The application starts and shows a toolbar - which is a DBI Tech ActiveX control. If the DBI Tech Active X control is not installed or damaged, the application would simply show and error. The application does not know that there is another EXE that installs the DBI Tech ActiveX control. Usually if the application shows an error, customer reports it to me, and I tell them to run the SETUP.EXE which installs the DBI Tech ActiveX control. Now when the application starts, it AUTOMATICALLY starts the SETUP.EXE (the program that installs the DBI Tech ActiveX control). But nowhere in the application there is a code that points to the SETUP.EXE.
>Does it explain how it works?

dependencies
The DBI Tech ActiveX control might depend on other stuff installed, for example C++ dll or something like that. So your control might be there, but not the dependencies. I will not go into detail what possibly can go wrong here - but using Inno

So we see the Setup for the ActiveX starts, as soon as you start your app. Does your app sets anything related to this ActiveX at startup? Can you somehow trace until it starts? Or is it before the first line of your main

What you can do is asking the developer of your ActiveX for the dependencies (files, version), and check on customers comp.