Image preview

Question

I have some files with rvt extension that when i click on them i can see a preview image on the explorer.

Well now it seems that some program exposes certain code so as to render the file to an image and explorer gets the image and shows it.

How can i reproduce an app so as to use the exposed code an show the image?

Is it via DDE?
I saw I have a revitpreview.dll that is used when i click the file?
How can this dll be instanced?

Thanks