Sony Vaio gets Randomly thermal shutdown

I'm having Sony Vaio GRV-550 laptop, on which i had install Windows Vista as my operating system. It works fine for some certain time and then it get suddenly switch off. Then it automatically reboots and after few seconds it keeps on getting randomly thermal shutdown on my laptop. Can any body tell me that why i'm having such problem on my laptop? What's wrong with my Sony Vaio laptop? Is there any kind of hardware problem or facing some system heating problem? Can any body help me out to get rid of the above issue? Any kind of help on the above issue would be appreciated.

This shutdown problem could be caused by a defective thermistor on the logic board. A thermistor is a type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature. If the thermistor is not working properly, it most certainly could trigger a shutdown.

The unstable voltage supply to the cpu will still be there, but as my experience has shown, this won't harm your cpu. All we have to do, is to disable the ACPI functions that are shutting down the laptop.

Follow the below steps mention in order to resolve your issue.

1) First, try to run a spyware-removing program such as SpyBot Search & Destroy. If the computer still shuts down after a while, run msconfig and disable all of the programs in the Startup Group. If you know how, you can also do some registry edits that will stop things from automatically loading and executing.

2) Either unplug the cooling fan that sits on top of, or adjacent to, the CPU, or put a little piece of folded cardboard in the fan blades to prevent them from turning. Blast canned air in through the exhaust slots on the back or side of the machine to remove dust from the CPU radiator and fan. Plug the fan back in. Make sure the fan will turn freely (sometimes a dust bunny will hide in it). When you're using the computer, always be careful not to block the intake slots on the bottom or sides.

3) Remove the fan and heat sink, clean out the old (probably cracked and fried) thermal compound between the heat sink and CPU, and install new Arctic Silver 5.