The problem with .xv format is that it is a proprietary format used by a Chinese website to deliver purchased movies. If you try to run the file in another player in another country it will simply not work and conversion is out of the question because these files work in conjunction with another proprietary player which is available to customers only. I believe this format is not conversion ready.
For more information, please visit the Microsoft's Answer website. The last comment on the page states exactly what I mentioned above.