>As I just described to Hank, the application EXE and the set EXE are two different programs. So, if any ActiveX components got wiped out or whatever, the main application EXE would show an error. The main EXE knows nothing about the SETUP.EXE

Are you sure? If the setup was generated in anyting using m$'s tools (forgot the name, just that it uses .msi extension), then it wrote in the registry which setup installed the app, so yup, the app itself wouldn't know, but Windowses would. Happened exactly the same way each time we had that. And mind you, our setup was generated in Inno, except the runtimes setup, which was a .msi - and then it went that way.