If your laptop turns off unexpectedly, the most likely reason is overheating, but it can also be due to a power overload in the AC adapter, intermittent short circuits and less likely, an operating system problem or virus/spyware.

If you have time to do this before it shuts itself off, perform a quick spyware and virus scan. If you cannot do this, try it again in Safe Mode (restart the laptop, press and hold F8 and select Safe Mode from the menu). If the laptop doesn’t turn off in safe mode, then the problem is probably not caused by hardware. While in safe mode, remove spyware and viruses and clean the registry (check my Resources page if you need free cleaning programs).

I assume the laptop will turn itself off even when in safe mode, so the problem is probably due to overheating. First, check whether the battery has anything to do with this. Remove it from the laptop and work only with the AC adapter. If everything is ok, then you need to replace the battery. If it still shuts off, then try to work only with the battery, without the AC adapter. After this test, you’ll know if you need to replace the cable with the AC adapter.

Most likely reason is overheating of the processor. To test this, download a CPU monitoring program such as Real Temp and check the temperature while you work with your laptop. To test this option further, work in an air conditioned room and see what happens. Turn the laptop upside down and inspect the CPU fan. If you see that the fan is clogged with dust, then a simple cleaning of the CPU fan could solve the problem. Blow compressed air into the fan and make sure there is no dust left. You can also use a thin brush. This solved the problem in my laptop.

Sometimes the CPU fan can stop working and you have to get professional help to replace it. Also, if the laptop still short circuits after all these tests, you’ll have to send it to a service center.