I wanted to make a simple .wav file for some testing. I decided to use the Sound Recorder that’s been in Windows for awhile.
Your only option for saving from the built-in Sound Recorder (assuming you’re not using the “N” edition for Europe et al) is WMA now – you can’t save as .wav any more.
The help spells this out, but their phrasing of “By default” made it sound to me like there would be an option for .wav (and not just that the N editions used .wav still).
Scanning around for something simple to convert the .wma files to .wav’s, this one seems simplest and least intrusive as a command-line app (that I can therefore most easily script).