First, if you have color coded jacks at the back of your case, make sure the microphone is plugged into the pink jack. Go to control panel, switch to classic view if not already done, Sounds and audio devices, press the Advanced button that is into the device volume panel, if you see the microphone slider skip what is in brackets
( options, properties, check microphone, press ok ), make sure it is not muted and you can play with the volume slider there