Hi, and Welcome to Linux and LQ !
This may seem dumb but; did you check if your volume is not muted, or if the cables are plugged.
Believe or not, this is the most common cause for sound problems
To check if it is not muted do this:
Open a terminal, and at the command prompt type of this: alsamixer, aumix, or kmix, then check that it is not muted,
in alsamixer and in aumix to mute or unmute press [M] .
Also, i have to turn all up the VIA DXS to listen any sound.
Hope it helps