I have and Intel 4 desk computer thats about 2 yrs old. I am not very good with computers so this is pretty basic, but the tower part of the computer constantly hums like the fan is on ALL THE TIME! It never has done this before, it just started recently. Nothing has changed, its not dirty or dusty, there are no program problems, but it drives me bonkers. In the past the fan (or whatever) has come on for a few minutes, but then you wouldn't hear it again for like an hour, now, like I said, its on all the time. Any suggestions?? Thanks.