I've already uploaded a video following the right instructions and the problem is I can't play it. I don't know if it a problem with the plugins, even though everything seems right. The picture below shows the preview, but once I click on the "play" button, nothing happens.
Thanks a lot for your answer. I've already tried to play it after inserting it, but it simply won't open. I don't know if I have to fix anything else. I also uploaded mp4 videos, to check if the mistake was the extension, same hopeless result!
I think I recognise what is going on. The VLC media player plugin has taken over the playing of .wmv files and fails to do so. I had the same on my windows PC at work using Firefox. Internet Explorer worked fine. To solve it I changed the file association for .wmv files back to the default Windows Media Player (Options > Applications > search for wmv).
I suspect the same would apply to mp4 files. I'm not sure what it is with the VLC plugin but I didn't have much success with it so far.
Thanks a lot for your answer. It's very true that .wmv won't open if using firefox, the same video opened with IE. However, I've tried uploading an mp4 video and it works fine. So the problem seem to affect only .wmv files.
Now, the thing is, I don't get your instructions as to the default Windows Media Player. Where do I have to change that? What options am I supposed to edit? (I'm an ignorant!)