Laptop shut down randomly when temperature is low

[Kai Di]

Hi, I have a 3.5-year-old Samsung RF411 laptop.
Recently, it randomly shuts down without any warning.
Sometimes, it's blue screen or the screen gets blurred and laptop halts.
Initially, I thought maybe it's getting too hot (I live in Singapore).
So I cleaned the fan and changed the thermal grease.
After that, I closely monitor all the temperatures.
But it still shut down randomly even when the temperatures are quite low.
For example, CPU temperature <60C, graphics card (GeForce 525M) <50C.
The T_junction of my i7-2630QM cpu is as high as 100C.
Moreover, when I'm playing games, the cpu easily heats up to around 90C, but everything is just fine.
Ironically, it sometimes shuts down when I'm doing nothing and the laptop is quite cool.
So I conclude it's not a temperature problem.
Sometimes, it shuts down a few mins after booting, sometimes a few hours.
I cleaned my RAM and it does not solve my problem.
I believe it is a hardware problem, because it happend a few times that it shut down even just in BIOS (I've never updated my BIOS before).
I'm really frustrated now and don't have any clue.
Has anyone encountered similar problems? what should I do?

 

[Im Spartacus]

Go into power options in control panel, look at your set power option select it, then select change advance power options,select processor power state and up your minimum setting.