You experience problems with sound after you install Windows Vista Service Pack 1

All:

Taken from the Microsoft Vista site.

After you install Windows Vista Service Pack 1 (SP1), you may experience one or more of the following problems with sound:

• No sound is produced when you play audio files or run programs that have an audio component.

• The speaker symbol next to the clock in the notification area may display the following message:
No Audio Output Device is installed.

• The Sound Controller in Device Manager displays a yellow exclamation point.


Refer to the following link:

http://support.microsoft.com/kb/948481