This applies to Dell systems that use the on-board SigmaTel audio device,
particularly XPS systems, but it may work for others, as well.

When I upgraded from XP to Vista Home Premium, my sound worked fine. Running
the Anytime Upgrade from Home Premium to Ultimate, however, knocked out my
sound. Here's what I did to fix it:

--Go to Add/Remove Programs in Control Panel. Uninstall anything that says
"SigmaTel Audio". This will uninstall both the application *and* the faulty
drivers. (I only had one line item to uninstall, but depending on your own
configuration, there may be others.)
--Restart your computer.
--When you're back at your desktop, Windows Vista should discover your audio
device. It will give it a generic designation, such as "High Definition Audio
Device (SPDIF)", or something similar. It will now show up in Device Mangler.
At this point, you probably still will not have sound, but what's important
is that Windows now recognizes your sound hardware.
--Go to this site and install the latest Vista drivers for your sound device:

http://support.dell.com/support/down...&fileid=195629

Install the drivers, restart your computer, and you should have sound.

I hope this helps. I know how frustrating this issue is. If this fix works
for you, let me know!