I have no audio driver installed in my Hp Pavilion

Hello,

My pc is a HP Pavilion dv6704nr Entertainment Notebook PC series
It has windows vista.
Since last year it had this problem for a little while, and i kinda fixed it, and i don't know how it actually got fixed. In the mid summer the problem came back and i tried downloading the audio driver from the website and still wouldn't fix. Right now its still no sound and has that little red x on the speaker sign. I may deleted the driver when i went on my hardware devices and it has not came back since, so whenever i try re installing it again it allways gives me an error message like this"Driver Installation Failed: Could not find the MEDIA device for this driver". I just did a system recover and it didn't work at all! Is there more ways to fix this? Please.