Go to Start , Control Panel, Sounds & Audio Devices open it up and check that you have not got the Mute box ticked

If it is clear go into advanced and make sure that none of the mute buttons in there are ticked

Aloso that the volume slider is well up the scale

Re-boot your computer again and let it fully boot up. Volume control may come back if not go into control panel and into sound properties and activate the sound icon in task bar