Why does my webcam microphone not work? :(?

i have a windows vista computer and the microphone is inside the lap top i don't understand why when i record something on my web cam and play it back you can't hear the sound. I accidentally uninstall the sound system a while back but i re-installed it using this website and now the speakers work fine and so does the audio but i don't know if it damaged the microphone or what? can anyone help me figure out how to fix this problem please