HP G60 audio cuts out of speakers but headphones work fine

Greetings - 

I was given this notebook PC by a friend.  OS is Windows 7.  When a sound plays from the system, I hear it over the internal speaker for perhaps 1/10 of a second, then it cuts out.  If I change volume level, I'll hear the sound *while* I am changing the level not once I stop moving the volume slider.

Meanwhile the headphone jack works fine - headphones have no issues and work 100% of the time.

I have already uninstalled the Conexant speakers and rebooted, with no change in status.

Any suggestions?  Many thanks -

Richard C. / Allentown, PA  USA