Update your sound card.
How to do?
Here it is a few easy steps.
1. Click Start
2. Right click My Computer and select Properties
3. Click the tab labeled Hardware
4. Select Device Manager
5. Expand Sound, video and game controllers
6. Right click your sound driver and select Update.
If you your computer cannot update on it's own from that, write down the name of your sound driver.
Google "[Name of sound driver here] Update".
The website should be straight forward on what to do.