C# activex dll issues

I'm having the worst time trying to do this (http://www.z****oft.com/zmud/complug.htm) in C#. This article is sound, this works fine in VB6, but I'd rather not have to write this in VB6.

Do I have any hope of getting this to work in .net? Every .net dll I create is not recognized by the application, it just says "invalid" dll file.

Using visual studio 2008, I create a new Class Library Project, add a reference to the entry "Zmud Library" on the COM tab of the add references window, then I add my using Zmud; and inherit my class from : IzMUDPlugin and explicitly implement the IzMUDPlugin Members using the right click menu item. The dll file compiles fine. (I have the project setup to register COM interop and expose to COM as well.) However when I attempt to load the dll file the host application does not recognize the dll file and will not load it.

The VB6 dll file I created by following that article works fine.

Please tell me this is possible in .net, I don't want to use VB6.