The Sound Recorder provided with Windows 8.1 is totally primitive and records in one format only and saves files in the absolute most obscure place possible. Ignore it.
Google Audacity and you'll find a hugely capable audio recording application which is FREE and works like a charm. You can export any recording you make in many different formats. Don't forget to download and install the LAME program you'll see as a helper program. You can edit any kind of audio file and change it in many incredible ways. Install it and put a link onto your Start menu. You'll get great use from it.

Also: my advice is always "Nov shmoz ka pop!"