I would imagine that there are many programs that can create dll and exe files.
You can create dll and exe files yourself, quite easily if you install the .net framework, and then use a text editor to create the file. You then access the compiler that comes free with the framework to create either a dll or exe file. You can even view these files with a viewer that comes with the .net framework. I think you can tell what software created the files with the viewer. I did have a link to a webpage which explained how to do this, but I cannot find it! If I do come across it, I will post it.
