I have a Dell 1525 and before I had used 7 I was using Vista. My audio driver was the SigmaTel 95XX C-Major HD audio. When I up graded to 7 the sound was fine except after boot up I would get the message "Audio Service is not running" even after reinstalling the driver.
Then my line input was...
audio
boot up
c-major
configuration
custom install
dell
device management
driver
hd audio
lineinput
microphone
realtek
service error
sigmatel
sound issues
support
troubleshooting
upgrade
vista
windows 7