Morning all. I'm hoping someone out there will be able to assist me. i upgraded to windows 10 a while ago. All of a sudden my sound does not work anymore. i have a Dell Lattitude 3540

 Upon further investigation I found the speaker icon is shown with a Red "X", and when I hover the mouse over it,  a message of "No Audio Output Device Installed" would appear. T As far as I'm aware there's been no software installed that would have lead to this problem.

Working with computers a lot, I know my way around, so I then went to Device Manager to look for any faults. I looked under the "Sound, Video and Game Controllers" and found only Bluetooth Audio was listed, which I thought was a little strange.However under the "System Devices" section I found that the Realtek High Definition Audio Device had a yellow exclamation mark over it. Selecting it revealed it had failed to start (Code 10). Suspecting this was the root of my problem, I tried to Update the Driver. After a while of checking online, the message received back informed me that the installed driver was up to date, therefore it couldn't be updated, not what I wanted to hear! 

I've asked Google for other solutions, most of which amounts to reinstalling the sound driver, which I've tried but nothing seems to work. As a last resort I ran the Diagnostic tool from the Bios Menu, and everything passes correctly, yet I still have no sound from the laptop speakers.

PLease advise