Some time ago I was asked to fix a Pentium 4 PC.  Initially, its symptom was that it would shut itself down spontaneously a few minutes after launching Internet Explorer.  So the first thing I told the user was to use Firefox instead.  Firefox didn’t cure the problem, because it really is a hardware issue instead of malware installed on Internet Explorer.

Replace Power Supply

I have to suspect the power supply being the culprit, because it’s been used for 7 years, and a faulty or dying power supply is capable of producing this kind of symptom.  More importantly, among the several possible causes and their associated repairs, changing the power supply is the easiest.  One day after I changed the power supply, it is confirmed that the problem remained.  And it had gone worse, the shutdown occurred a few minutes after booting Windows, regardless of whether she launched a web browser or not.

Replace CPU Heatsink Fan

Then I discovered from BIOS that the CPU temperature is abnormally high.  So this explains the shutdown – it is likely a thermal shutdown by the motherboard.  The strange thing is that the CPU fan did not seem to be faulty – it was operating normally.  Anyway, I had to replace the CPU Fan no matter what.  To do that I needed to clean the completely dried up thermal compound on the CPU (and the old spare heatsink for replacement), then reapply fresh thermal compound.  After doing all these, however, the temperature was still abnormal.

Replace CPU

Finally, I changed the Pentium 4 CPU.  Then the temperature went back to normal, and the PC worked normally.

This result is a little surprising to me.  When the replacement power supply didn’t fix the issue, and before I found that the CPU temperature was abnormally high, I thought it must be the motherboard.

Among the many components of a PC, I have to say that the Intel CPU must be the most reliable component of all when installed and used properly without overclocking.  This is only the second Intel CPU that I can witness dying, and I suspect in this particular case it is not accidental.  The heatsink compound that was originally on the CPU was applied really unprofessionally.  My theory is that the badly applied heatsink compound, being dried up, killed the Pentium 4 CPU.