Every time I have my computer on anywhere between a half hour and hour or longer my computer starts making a really annoying humming noise that wont stop until I shut the computer down. If I turn it off and turn it right back on, it still does it. I have to let it rest for a while and then turn it back on before it will stop. Could this be my hard drive going bad, or could it be something else. Are there any other symptoms to look for or anyway of finding out exactly what it is?