Sound doesn't work after start up

I have a Dell and Windows Vista and after the initial startup of my computer my sound doesn't work, sometimes after I restart it a few times it works, but most of the time that doesn't work.

Hi,
Please download Microsoft Fix It from this link :
http://go.microsoft.com/?linkid=9740814

Save to your Desktop, Run it and follow steps in the wizard.

I did that and it said that it did not detect any issues common with that problem dealing with the speakers.

Hi,
check Speaker cables. You should unplug it and plug in some MP3/MP4 player to check if speakers work property.