Thumbnails, when uploading files

[kittykat8103]

I'm not sure if this goes here or not, but when I upload a video file or a zip file they upload fine, but they have no thumbnail. The video file has an image with "WMV" and zip file has image with "ZIP" for thumbs. I'd like them to have an actually image, how do I do that?

[Joachim Müller]

RTFM