What OS and Soundcard?
Are you recording?
if so, do you see a wave form within the software?
Where are your headphones plugged into?
Are you using an outboard mixer or a pre-amp?
try this.......
on the task bar on your desktop hit
start
controls
control panel
Audio multimedia or Sounds and Audio Devices...
click on the audio tab..
under recording...hit volume...
make sure that your mic in is selected and not muted for recording...
you can also get here by double clicking on the small speaker icon on your desk top task bar (right side....)
If it is Creative software, you might need to use the Creative task bar...Same same for M-Audio.....
good luck man....
Joe