I am unable to run WMV videos in firefox in both linux and windows even after installing wmpfirefoxplugin in windows and mplayer in linux. Actually first i tried in Windows, i found searching at forums that three dll files must be missing from "program files\Windows Media Player":
npdrmv2.dll
npdsplay.dll
npwmsdrm.dll
I downloaded these files and video started working in Windows. But in another system, it is not working even afer installing wmpfirefoxplugin and downloading these three dll files. And in Linux it is not working even after i installed mplayer plugin. What should i do then. Should i change the source code of my website ? I have tried all the MIME Types also in the code, but none of them worked.

Have you tried installing VLC?
VLC will play just about any multimedia file-type.

There is a VLC browser plugin available for Linux, but I can't remember if it is included in the installation of the main VLC player package or if it is a separate package. Best bet would be to take a look in your distros software repositories and see what VLC packages are available.

You could either do this graphically by opening up the GUI for your distros default package manager and set a search filter for vlc, or use the command line to search. So, for example if you were on a Debian based system you could use apt-cache search vlc on the command line to list all packages in the repositories related to vlc.

Yes i have vlc plugin also installed in the web browser. But still it is not working.