hello... i have a problem here.... i have already use this computer for about 5 years, and now i have a sound problem.. started 1 week ago, everytime i open some website and playing games. the sound just suddenly off. i don't know why. first, before i open the website and playing games, the sound worked just fine. but, after i have reboot my computer, the sound on again... but still, when i open the website and playing games, i lost the sound again... any help???? thanks