1. Get a better microphone. Don't settle for one of those cheap $1 ones. They
rarely have good quality.
2. When recording narration, you can change the quality, but you can't
remove the hiss.
So, I suggest that you download Audacity:
http://audacity.sourceforge.net/
Audacity is a *free* sound recording/editing program that allows you to make
and work with a sound.
Once you download it, click the red circle button to narrate (don't start
speaking for two seconds), and click the yellow square to end narration.
Then highlight the two seconds you left blank, then Effect, Noise Removal.
Click Get Noise Profile.
Then highlight the entire recording, then Effect, Noise Removal, Remove Noise.
You can delete the two seconds now.
Save it as a sound file (probably in WAV format), and Insert it into your
PowerPoint.
Happy holidays!