i'm not very computer savvy. today i noticed i did not have any sound on my comp. its an hp pavillion dv 6500 using Windows Vista. when i hover over the sound icon at the bottom tool bar the message displayed is "no audio output device is installed." i have searched online for help but the suggestions tell me to go to "device manager" then find "sound, video, and game controller" but that is not even displayed in my "device manager." please help.