It's not clear whether your laptop doesn't have sounds at all or if only there is no sound on playback videos you've recorded via web cam built-in in your laptop. If the later is the case, check your mic if it's working or not. Go to control panel and search for the sound option then try to check you mic or you could use the sound recorder program accessed via Start>My Programs>Accessories for Window Vista Users. If you're an xp user, there's a similar program. Then try to record and speak through the mic, then playback the recorded file.