Do the .wmv files have some sort of copy protection on them? If so, do you know how to remove it?
I don't see that it would be any easier to go from .wmv to mp4 than going from mpeg2 found in dvds personally. The mpeg2 is also a "digital" copy you know.
You can use Xvid4PSP to convert .wmv to mp4. I believe MeGUI would also work.