Your fan will increase speed as the processor get hotter during more intense processing. When I use PHotoshop and start to do some heavy retouching the fan speed and therefore noise will increase. Don't Worry. It's just doing it's thing.
We purchased a HP Pavilion zv5330us in December. Today, it's making a louder than normal fan noise.... almost like a jet taking off..... this has not happened before - is there anything I can do other than shut it off?

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