Samsung Q35 - sound does not work

Question

The sound on my laptop has stopped working. Using a headset through USB works fine. When I go into control panel it all looks fine, but I hear nothing. I have plugged in external speakers to no avail.

I am using Vista. In control panel it tells me I am using Digital Output Device (SPDIF) and the drivers I find are:
dmk.sys
HdAudio.sys
portcls.sys
SysFxUl.dll
WMALFXGFXDSP.dll
Means nothing to me but I am hoping there is someone clever out there.

Durj