Windows 7: 'No Audio Output device is installed' Problem

Recently I've come across the problem of having no audio on my HP Pavilion dv9700 Notebook PC, it simply tells me that 'No Audio Output device is installed'. I upgraded my computer from Vista to 7 and for 5 months had no problems. I've tried to install things such a Realtek and also tried to Scan for Hardware Changes and Update driver software, but nothing has worked. Also, in my device manager, under Other Devices there are 3 yellow signs with exclamation marks in front of 'Coprocessor' and also in front of two 'pcouffin' devices, I have no idea whether these are the roots of the problem or not. Is there any way that I can fix this problem?

Welcome to the Forum.

Problem devices can cause a range of problems. You need to address them.

Take a read of this:
Coprocessor driver required

And This:
Pcouffin.sys Windows process - What is it?

And see if helps.