The heat sink fins are more than likely clogged with a mat of dust and debris.
(Try to get a hold of a service manual. Anything less than 10 years old is scary to get into and cleaning the heat sink may involve breaking the thermal bond with the CPU.)
(Try to get a hold of a service manual. Anything less than 10 years old is scary to get into and cleaning the heat sink may involve breaking the thermal bond with the CPU.)