Help! Computer microphone not working for program!?

I have just installed Talk to Me Spanish on my computer and a microphone is required for some of the phonetic exercises. The microphone works because I just made a voice recording on ym computer and listened to it. The program, however, isn't recognizing that I'm speaking and thus I can't go further along in the program. It's like the program isn't recognizing the microphone even though it's hooked up and running. What should I do? Please help.