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?

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.