Things to try :
- Ensure that the Mic is connected to the right port (pink colored)
- Run the Microsoft sound troubleshooter
- Check Windows Update, optional section, for any driver updates
- If no updates were found, check the computer manufacturer's support website for driver updates to the audio device and to the chipset
- If the computer came pre-installed with a sound studio, check also for updates
- Check also for a BIOS update (to install with very great caution)
If nothing works, let us know the computer model, sound card model and driver details.