Update ATI Audio or Sound Driver
Most computers come with ATI Audio Drivers pre-installed at the factory though bargain computers may not have the best sound cardon the market.
Whether you want to replace your existing ATI Audio Drivers or install a new one, you will need to also install a ATI Sound Driver at the same time. Another instance where you might need to add a audio driver if your current ATI Sound Card starts acting up. (More Informations about ATI Video Drivers)
By restoring the ATI Audio Driver, the computer once again recognizes the device and the sound card begins working again.