no onboard sound with Soltek SL-75MRN

Hi-
I have a Soltek SL-75MRN Nforce2 motherboard on which the onboard sound
seems not to be working. I have enabled it in the BIOS and loaded the
correct drivers; everything is recognized and being reported as working in
Device Manager and no problems are reported in the Nvidia sound mixer applet
that is supposed to allow speaker configuration, etc. When I play sounds,
the sound level indicators move, but I hear nothing. I have tried a set of
headphones, a new 5.1 speaker surround system, and my old set of powered
speakers (which I know work), and nothing.

Anyone have any ideas?

Thanks.