This problem is my own on by Acer desktop with Win 7 64bit. I wrote before that when I start up my computer there is always a red mark on my speaker icon. I have to click on it to open the volume bar then click on the blue volume symbol to mute the sound and then click on it again.
Yesterday, it didn't work. Instead a Window's troubleshooter popped up and when finished it displayed a box that read:
Windows could not start the Windows Audio service on Local Computer. Error 1068: The dependency service or group failed to start.
A bit of search online and I had to make sure four services where started
Multimedia Class Scheduler
Plug and Play
Windows Audio Endpoint Builder
Click Start, either go to the Control Panel or type Services.msc in the Start Search box. Scroll down the list of services, find each of the services listed and double click on it. Set it's Startup Type to Automatic, if not already. If it's not started click on the Start button. Note, if it's not started and not set to Automatic, set to Automatic, then click on the Apply button and you should then be able to click on the Start button that otherwise might be unusable.
That should clear it out.