Hi,
- Was it working before?
- Have you made any changes to the computer prior to the issue?
Method 1:
I would suggest you to connect the headphone to a different computer and check with the issue.
If the issue still persists after connecting to a different computer. I would suggest you to contact the hardware support for further assistance:
Microsoft Hardware
http://www.microsoft.com/hardware/en-us/p/lifechat-lx-1000#support
Method 2: Run the Hardware troubleshooter and see if it helps.
Open the Hardware and Devices troubleshooter
http://windows.microsoft.com/en-US/windows7/Open-the-Hardware-and-Devices-troubleshooter
Also refer the links:
Tips for fixing common sound problemshttp://windows.microsoft.com/en-us/windows7/tips-for-fixing-common-sound-problems
Troubleshooting: Headsetshttp://www.microsoft.com/hardware/en-us/help/support/troubleshooting/headset/hardware-issues
Hope this helps.