What is the most efficient way to convert a .wmv video?

[joe at actionline.com]

> I left this part out of my description, but did you click on
> "Source" and select the video you want to convert?
> Brian Cluff

That did the trick. Guess I should have figured that out.
My first try was on a file 25-meg (25,706,036) and the
result was 8-meg (8,180,441).  Excellent!  Thanks!

But I am curious why handbrake assigned the suffix ".m4v"
instead of .mp4 (or .mpeg)?