Sound problems with laptops and desktops are often due to a missing or corrupt driver. Reinstalling the sound card's driver may fix the problem. Basic troubleshooting including checking the computer's volume and ensuring the mute setting is not enabled should be completed before investigating the sound card's driver.
Hardware drivers provide the interface between the sound card and the computer's operating system. Drivers are created and are available for download from the sound card's manufacturer. New computers that come with an operating system include drivers for all installed hardware. Sound card drivers sometimes are corrupted as a result of operating system upgrades. In this case, reinstalling the driver may fix the problem.
Installing a new operating system or upgrading to a new major release can also cause the sound card to stop functioning properly. Upgrading from Windows 7 to Windows 8, for example, may require installation of a new driver. In most cases, however, hardware that works on a previous version of Windows will work on new releases.
If the problem is not related to the driver, the hardware may be faulty. Sound cards sometimes break. The connection between the sound card and the motherboard is another point of potential failure, as well.