Step 1.Disconnect all external speakers and headsets.
Step 2.Click Start > Control Panel> Sound > Speakers and Headphones, and then click Configure.
Step 3.Click Test to test that sound is audible from the built-in speakers.
If that doesnt work try this
Step 1.Go to Start/window and righ-click
Step 2.From the list of results click device manager
Step 3.In Device manager under sound, video and game controllers, select your sound card open it
Step 4.Select the Driver tab, and select Update Driver.
Step 5.Let it download automatically
Step 6.Then reboot system