The file has been incorrectly named as .wmv when it is not a .wmv file.
Use SUPER from erightsoft (free software) to look at the properties of the file and find out what kind of file it really is, then rename it with the correct extension. You need to have “hide extensions for known file types” disabled in Windows. http://www.wikihow.com/Disable-Hidden-File-Extensions-in-Windows-XP
For information about working with DVD’s have a look at the Doom9 forum.