Have you got the volume icon in the bottom right of your screen? If not, you'll have to go to Control Panel via the Start Menu then choose Sounds and Audio Devices.
Double-click the volume icon to see the Master Volume box. Go to the OPtions menu and choose Properties. Change the Mixer device to the input one for your sound card,
Make sure that the microphone is ticked and check the Options and Properties for this. Make sure that microphone is chosen etc.
Hope this helps (recording is very often set to CD).