Ok, I'm trying to retrace your steps.

I think I understand the lite-c script you C/P in your post: according to the value of command_str, your application either displays a preview, the level or a configuration panel. From what I gathered on a few web sites, these options are a requirement for windows to consider an application a screensaver. So far so good.

I am stuck here however: where does the wdl file you mention enter the picture? How can I mix c-files and wdl files in a single project? Is it in the wdl file that command_str is set? How does Windows set the value of command_str?

Thanks again for your help and patience.