There should be a loudspeaker icon at the bottom in your task bar, click on it to open up the soundcard mixer. You should see sommit like a mixer with sliders with a check box next to each one. You need to go into your recording section of the mixer and either adjust the slider of the mic up to 2/3rds of the way up OR tick the box next to it to enable. You should now be able to record oure WAV on to your hard drive and then convert it to mp3.
Andy