Just because something is a ".dll" doesn't mean it has to be registered. Only ActiveX DLLs would need to be registered. Since this is VB.NET code, I'm assuming that what you're tapping into is a .NET Assembly, which doesn't need to be registered. You can find out if the file exists, and if so, use reflection to load the assembly and then get a list of all the classes in it and test the results to make sure that "FitManager.CFitManager" exists.

-tg