I would likie to report that my original issue DID respond to the following:
There is a situation where the test will pass even though there is a hardware problem. If you have the following combination of symptoms AND you have an HD audio chip
* Speakers don't work
* Headphone jack does work
* Reinstalling audio driver does not help
* Audio test in Dell Diagnostics passes
then there is the possibility of a failed sense pin in the headphone jack. This will pass the Dell Diagnostics test but will continue to show symptoms when you boot back into Windows. To learn how to complete the diagnosis of this problem see the faq "Headphone Jack Works But No Audio From Speakers".
Dell, after 5 months of emailing, finally broke doiwn and reoplaced my mother board where the sense pin is evidently housed. The speakers, after not working for 7 months, finally came back on line!!!
Thanks for posting this FAQ. It helped, eventually.