It could be a problem with audio drivers, please tries checking the audio in safe mode. To enter safe mode follow the below steps:
Check if the computer is doing the same thing in safe mode with networking.
If the problem still persists,
Try the above steps and reply for further help.
Thanks & Regards,
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The headphone jacks work OK but no sound comes from loudspeakers.
Re-install the Sigmatel audio driver as advised by Nikhil D. Note that there is no Sigmatel driver for Windows 8 so what you should do is download the Sigmatel R171786 audio driver for Vista, then install it into 8 by using Vista compatibility mode.
If that does not fix the problem then you probably have a failure of the sense pin circuitry of the headphone jack. See the Headphone Jack FAQ for details about the issue and how to diagnose it.
Many thanks. When first I tried it said no suitable drivers for Windows 8 but then found the driver referred to above and confirm it now works. Many thanks