error showing audio device not installed

I have this problem, it shows audio device not installed. The sound comes and goes as it pleases. When you start the computer, some times the sound is there, but within minutes the sound stops and no sound device installed. i cannot see any sound device in the device manager when this happens.
I have a HP Pavilion DV6700 entertainment notebook. It has some conxanent sound or something. Windows Vista operating sysytem.

If anybody can help me on this I will really appreciate it.
Thanks

 

Take a look here, I think the drivers are good for your model.