|Have you tried uninstalling the drivers and then updating later on ?|
First of all you have to determine if its a hardware or a software issue.
1. you could check this by tapping on the bottom of the laptop gently in the area just below the speakers. If there is a loose contact this procedure can help us find it out
2. How about the Logon sound. Is it OK ?
3. Are you trying to use the quick launch (volume) on the right hand corner of your laptop just above your speakers to increase the volume. Have you tried the volume icon instead which is within windows to adjust the level ?
4. try plugging in a headphone to see if the same happens while you listen through it.
Let me know the status after you check these... reply back to this post.