How long have you had it?
Have you opened any bays (the easily opened bays on the bottom side that house the CPU/RAM/HD/etc, assuming that has them) and blown out the dust?
This is CPU temperature we're speaking of I'm assuming?
It sounds more like the heat sink could have come loose or you have zero airflow from dust buildup. 100C is a hard temperature to reach with proper airflow and a properly seated heat sink.