Mike,

>So NUnit is altering the behavior of the application. I notice that the mmApplication.exe.config file exists - at what point is this placed in this folder? Would it be just a matter of making a copy of it with the other name? (which is what I'll try next).

When you rebuild a project that has an app.config file, VS .NET makes a copy of the app.config file and renames it to the name of your project's output file plus (with an additional .config extension).

Regards,