You need a codec that handles m4a and gets installed to the system.

K-lite is one for windows, but make sure to download it from a reputable source.
I have heard of some sites 'adding to it'.
As always, scan it before installing, regardless of which way you decide.

FWIW, Quicktime isn't as bad as the old days. I think you get more control when installing now, for one. So it doesn't try to take over everything like it used to.
Pay attention to options along the way installing it.

Suppose you could also try an online m4a to wavefile convertor .. but better to have a codec installed that can do it for you.

I do not work here, but the benefits are still awesome
Make your sound your own!