Check computer's internal hard drive to confirm it is an Apple-installed part. Compare hard drive information in System Information (System Profiler in Snow Leopard) to the Apple Hard Drives Matrix in Apple Support article SM155: Hard Drives Matrix to determine if user's installed drive is one of the OEM drives available for this computer configuration. Note: Third-party hard drives outside this product's specifications, and without correct firmware, may cause computer to run hot. In such cases, inform user that computer has been modified from its original, supported configuration, and such a repair would not be covered under Apple warranty.
Reset SMC using the procedure listed for this computer in Apple Support article HT3964: Intel- based Macs: Resetting the System Management Controller (SMC).