OP, this is why you post in the Computer Megathread instead of a new topic.
You get idiot replies like these:
Pour water on it to cool it off.
HPs and Compaqs have been known for heating problems. Solution? Don't use an HP or Compaq laptop
Anyway, sounds like one of two things.
Sounds like either a cooler/heatsink has come loose, or the thermal grease has worn out on one of them, or a fan has failed, and/or gotten dust in it.
When using a laptop it is best to buy a cooling pad, for minimal dust intake and maximum cooling efficiency.
Turn it off and let it cool, And if you're feeling brave* open it up and blow out the fans and such with a can of compressed air or a air compressor.
*I say brave because my dad's taken apart quite a few laptop to blow them out and he's always had trouble putting them back together properly afterwards, So if you do open it up be sure to take very precise note of where everything was.
This is a good first move. Don't vacuum it; it can ruin your components. Always blow (compressed air is perfect).