The VideoLAN Forums

Hello,
How to change the preview image for the videos that shows when you have on the "largest icons" in the folder?

These previews are generated automatically by Windows (See http://en.wikipedia.org/wiki/Windows_thumbnail_cache). Afaik there is no tool existing with which you could modify them. And if you would change them, there would be no guaranty that the changes are kept, as Windows will update these thumbnails from time to time.

as Windows will update these thumbnails from time to time.

not simply from time to time, but each time you open the folder with these videos

I doubt that as this would make the Thumbnail cache useless.