This is a hard one, as it could really be anything. Our previous question was very similar to this, so I'll give you similar advice. Step-by-step elimination. You say it only happens when gaming - does it happen in every single game? Have you tried re-installing Windows? Defragging your hard drive?
I would try disconnecting all of your external devices - speakers, ethernet cable (or turn Wi-Fi off), external storage, etc. Go down to just bare monitor, keyboard and mouse cables being plugged in. From there, test out a game in single player and see if it crashes - if it doesn't - reconnect things one by one.