Hello nt1972, see how to Set how Firefox handles different types of files, if you set it correct and the issue remains, you need to reset mimeTypes.rdf in profile folder to clear the associations between MIME types and programs(a new file will be created on start up or when the application first needs to write to the file).

if you like see for more info : Opening files using plugins

thank you

that didn't help, because I did following the website said but I found the problem getting more badly, after I did what the website said that make my mplayer did pop-up at all before I done anything before I read that website the mplayer did pop-up but didn't play anything............

Try https://rajonlineradiotech.blogspot.com/2011/05/how-to-play-mms-and-rtsp-stream-in.html

that was for windows system, but I am using Ubuntu Linux mate

You posted this with a Windows computer, so I assumed that you were using Windows ,although I had noticed the mention of MPlayer (but there is a Windows version).

On Linux you need to register the mms protocol.

• http://kb.mozillazine.org/Register_protocol
• network.protocol-handler.expose.mms -> false