Windows 7: Random sudden shutdown while playing games

I have sony VPCF1 laptop, which worked fine until a month ago. Windows 7 home premium 64bits.

All of a sudden I started getting random shutdowns whenever I'm playing games. (namely Diablo3 and league of legends)

I used to play Skyrim on this laptop without any shutdown issues.
I suspected overheating problem, but the speedfan log just before the shutdown shows GPU at 80 C and CPU at around 75.

I cleaned out the heat sink and re-applied thermal paste anyways.
However, I clean the dust in heat sink every 3 months so there wasn't much to begin with. I also bought a cooling pad, which doesn't seem to lower the temperature at all.

I checked the hardwares using vaio care none of them showed known issues.

I am not very good with computers, but I've done everything I could to the best of my knowledge and through googling and I need help.

p.s In some of the posts in this forum people mentioned "minidump" to identify the problem. But I can't find it.
p.s2 In power management settings, it doesn't have cooling policy option. Is there a way to make it show up?
p.s3 The laptop doesn't experience shutdown when playing a high resolution movies at almost the same temperature as playing games.

Perhaps is just a matter of corrupt drivers... have you updated your audio and video drivers at all?

What do you mean with shutdown? Is it normally shudown so "logging off" and "shutdown" message on screen?
Or does it power off in a blink of an eye?

It shuts off as if I pressed on the power button long enough to do a force shutdown. And yes I updated all the drivers.

It's not a windows problem! If it was it should crash to BSOD (and automatic restart as you configured so).

When does this happen? Only when playing cpu intensive games? Only a long time after boot (when all components are cold)?

A component is too hot and BIOS monitors that. It powers off if too hot