Acer Aspire 4937G sudden shutdown

Hi everyone, I need some advice over here about this sudden shutdown of my laptop.
I had used this laptop for 3 years and I know why it shutdown suddenly, it's because of dust inside the fan.
I had called Acer to repair it during the 1st year and the 2nd year when I still have the warrant.
Basically, the repairman just replace a new fan for me.
Right now the problem I faced is that my laptop starts to shut down again, I clean the fan and even asked someone experienced to help me do the copper shim mod.
However, sometimes my laptop still sudden shutdown, this happened after the recent update for Windows 7.
I am not sure whether it was cause by the update or not, but my GPU temperature stays at 50, and I wanted to play games (blackshot), but when I just got into the game (have not even play yet), the laptop shuts down.
I'm running Windows 7, I heard that tweaking the bios can prevent this? Is that true, but how? And I'm not really sure if I installed all the correct drivers up, will this cause my laptop to shut down too?. Please help. Appreciate much

Anyone can help. My laptop sudden shutdowns again. Not playing games, Just browsing websites. Could it be my motherboard going to spoil? I wouldn't want to waste $80 bucks just to let Acer check ,and I m going army in few weeks time. So will not be buying laptop in the meantime