It could happen to you when you try to see some windows media player videos, you may not be able to play the videos in your firefox browser as windows.
In that case in order to fix this problem you will need to install the windows media player plugin for firefox to play these videos in firefox.
In order to install widows media player plugin, either you need to find the plugin with the automatic plugin finder service in firefox.
But some times plugin finder service in firefox is not able to locate the windows media player plugin for firefox [ as shown in the image below ] and displays the
"No suitable plugins were found. Unknown Plugin (application/x-player2)" when viewing sites with embedded WMP files.
In such a case, you would manually need to download the required DLL files and put then inside the plugins folder in firefox. Download Media Player Firefox Plugin Files from here
Path To Firefox Plugin Folder is – C:\Program Files\Mozilla Firefox\plugins
If the above method seems to be complex to you, then download installer which automatically installs the media player plugin in firefox, but make sure that firefox is not running when run the installation for Media Player Firefox Plugin.