Got little high spec but still lag when play game

So let me explain my problem, first, you may need to look through my spec (Below). I know it is not a monster for gaming but how can you image if half-life, Asphalt 8 and Minecraft make my PC lagged? Let be clear here:
+At first when I enter each game, it prety good, and some was awesome when it can easily hit 60+FPS (FRAPS)
+After playing a while(10-15 minutes), it start lagging a little and if I didn't close the game, just about 2 more minutes, the whole PC will crash.
I don't think dust cause this problem because I bough it a month ago
So can someone here who know please help me on this.
Here what I tried:
+Downgrade driver
+Defrag
+Update windows and other thing

Temperatures when playing Asphalt 8 in normal setting are about 50-53 (CPU only because for this game I think no need of nVidia card)

I solved my problem now, it was the BIOS, the last know good was 203 and I have 204, just simply go to the main page and start downgrading to 203. Everything is good for now. Thanks all.