I have the same problem as rafael my system suddenly shuts down by itself and when I re-open it will work normally but after a few minutes it will suddenly shuts down again may be 3 or 4 times it will happen before it will work continously. Sometimes I got the same message during rebooting process "CPU previously shuts down due to thermal event" but when I check the CPU or MOBOARD temperature in BIOS setting it ranges around 70 to 75 degrees Farenheit which I think is pretty normal. Is there somebody who can help us? By the way I have an INTEL Core 2 Duo Processor 2.8 GHz, Intel MOBOARD G31, 160 GB of HDD, 1GB of SIMMemory in a single slot. THANKS

Are you sure that it's 70 to 75 degrees Farenheit and not 70 to 75 degrees Celsius ? If it is Farenheit, then the shutdown temperature might be set way too low in the BIOS. I would check that if you can.

Please teach me how to check the thermal unit of my PC and how I will be able to change the temperature shutdown settings if ever it is in degrees Farenheit. By the way what is the normal thermal shutdown settings for PC in degrees Farenheit or Celcius? I also observed that if I install a software using the CD/DVD, during the process it suddenly shutdown.Is there any other hardware problem associated with this? or may be the power supply?

According to what you wrote-"I check the CPU or MOBOARD temperature in BIOS setting it ranges around 70 to 75 degrees Farenheit", you already know how to check the temperature. Just make sure it's Farenheit-that's easy to check. You should also be able to determine the shutdown settings under the same(or similar) menu in the BIOS. Not all cpu's are the same regarding the proper temperature settings, but 70 to 75 degrees Celsius would be too high.

Just right now, after all of those frequent shutdowns, my PC failed to reboot no blue screen this is the 2nd time I experienced it. Is the OS has been corrupted and need to reformat as what the technician claimed before when it was first failed to reboot? What about the sudden shutdown issue do you have any idea what causes it?

"What about the sudden shutdown issue do you have any idea what causes it?" You said that you recieved the message "CPU previously shuts down due to thermal event". That suggests overheating as a strong possibilty, or the shutdown temperature might be set too low in the BIOS. Of course it could be something else, but have you checked those things yet ? It seems more likely that it is hardware related, and not the OS as the technician suggested.

Yeah, you're right one of the strongest possibility is overheating, but the message appears infrequently that's why I still have a doubt about it. I will try to check and make sure about all those temperature stuff before jumping into other related issues. Can I consider power supply as one of the culprit? or may be the HDD? or CPU Fan?