The answer to this question for .wav recording is:
Click Start, open the run window and and type the following command to force windows to record as a ---.wav file:
run \soundrecorder /file yourfilename.wav
By entering the .wav at the end, the recorder will create .wav files instead of the default suffix. I use this command very often to record my voice for OUTLOOK, so that OUTLOOK rules can play the wav file of my friends names to notify me of important incoming email from a friend.
PS: I save the recorded audio files under the music folder and label the recordings to start with Email_nameexample.wav when used for Outlook so that when creating rules in Outlook, I know the recording is for Email. Hope this helps.