dmf1978 8 Junior Poster in Training

Hi friends,

I'm coding an application using VB.Net 2008 Express which work with images. It can save the results of this work in a file using an own format (not a regular image file) for future re-processing.
I wish to put a thumbnail inside the saved file, so it can show the contents in windows explorer thumbnail view (just as any other image file).

Where must I look? At the registry? I've to use an API? Really, I have no idea :(
Please, if you can give a starting point, I'll thank you so much.

Thanks in advance!
Martín