This is most likely just a volume control problem. The confusing part is that your sound card has two sound controls: one for recording and one for playback. You just need to make sure the playback volume is turned up and not muted. Double-click on the small volume control icon on your Windows taskbar and remove any checkmarks from under the appropriate volume control. Microphone playback volume is often muted to prevent your computer from broadcasting your microphone input.
If you do turn on the playback volume for your microphone, you should turn off your speakers and record with headphones to prevent the playback from "bleeding through" into your recording again.
keywords: monitor playback, monitoring recording, muted, can't hear it, overdub, overdubbing