I have a Dell Inspiron 9200 and had the same problem.
uninstall the driver, restart PC, then reinstall the original driver from
Dell, restart again. This fixes the headphone jack problem.

"Cassie" wrote:
[color=blue]
> Hi Joey
> i was wondering if your headphone jack is working now, if so how did you get
> it to work. did changing it to e1505 help or did you have a different way.
> i'm also experiencing the same problem and i also have the same type of dell
> computer which is dell Inspiron 2200?
>
> thank you very
> Cassie
>
> "Jeff" wrote:
>[color=green]
> > try the one for the e1505
> > workin fine here
> >
> > Jeff
> >
> > "Joey" <Joey@discussions.microsoft.com> wrote in message
> > news:AE638B13-C668-4E02-9BC8-C8648C07AAB5@microsoft.com...[color=darkred]
> > > no...a dell inspiron 2200
> > >
> > > "Jeff" wrote:
> > >
> > >> Joey,
> > >> Running a dell e1505 by any chance?
> > >> if so, the sigmatel driver on dell's site works good-
> > >> at least for me
> > >>
> > >> Jeff
> > >>
> > >> "Joey" <Joey@discussions.microsoft.com> wrote in message
> > >> news:A0F5CEB2-0BF3-42B6-90F6-E333B5E331A6@microsoft.com...
> > >> > After I installed windows vista, I began experiencing a problem with
> > >> > the
> > >> > headphone jack. Audio works completely fine, however, when I plug in a
> > >> > pair
> > >> > of headphones, the sound stops playing out of my laptop speaker but
> > >> > does
> > >> > not
> > >> > resume in the headphones. Instead no sound is heard. The speaker
> > >> > device
> > >> > is
> > >> > SigmaTel C-Major Audio. Like I said though, the speakers work fine.
> > >> > just
> > >> > not the headphone jack. What can I do to fix this?
> > >> >
> > >> > -joey
> > >>
> > >>[/color]
> >
> >[/color][/color]