Like lots of people I have struck the problem of no sound when I upgraded to Windows 7. I found the answer below on a forum to use the VISTA driver which I did OK and the sound works but it is real fuzzy. I tried both the OS32 and OS64 options but both the same.
Thanks
Terry
From previous
Go Control Panel then Devices manager.
Click on the Sound, video and game controllers option then right click on
the tab that opens below and select the current driver and then select
uninstall.
Go to Dell drivers and downloads page and find your system type and operating system.(In this case it
should be Windows Vista OS either 32 or 64 bit depending on your system since
there is no option for Windows 7.)
Select audio and then select Sigmatel -Driver. This should take you to a download page and then
download this driver (preferably in Explorer). Then install this driver by following the procedures then immediately reboot when prompted.