I am not sure of any free software that will let you do this, but I do know that you can purchase a copy of Xilisoft Video converter and make conversion changes regardless of the source format. You can find out more information about the software program at the following site:

http://www.xilisoft.com/video-converter.html

There are likely other programs out there that can do the same thing, so I would suggest doing some research before spending any money.

Darius Cubbage . Technical support analyst . Hosting.com