HP DV6929wm No Audio Detected Problem?

I'm having problems with the audio for my hp dv6929wm laptop. Windows does not detect and audio device and every time i go to update the drivers the installation stops because it can't detect the audio device. I've tried a million different things to get this fixed and nothing works. Going to services.msc does nothing for me. This is usually the solution everyone thinks will work. However every once in a great while after restarting my sound will work. It can work anywhere from a couple hours to a couple days. This computer originally came with windows vista and i upgraded to windows 7 at release. Had no problems until one day it just stopped working. Along with my cd/dvd drive. Neither are being detected anymore. Hope someone can help. Thanks

I'm having trouble finding the Motherboard manufacturer for this computer. I updated the bios a couple months ago to f.33 which is the latest for this model on the HP site. I've heard that HP sometimes doesn't update things on their site properly so there might be another bios update that i can't find. I downloaded a bios updating program and it said it detects an update for my bios however you have to pay to get the update. The last thing want to have to do. Thanks for the replies and can't wait to try more.