Laptop crashing whenever I play games and connect to a monitor

[seanng.alt]

My Asus laptop with a 820M graphics card crashes whenever it is connected to my monitor (hdmi) after around 20 mins. It runs fine if it isnt connected to the monitor. I have tried swapping hdmi cables and the monitor but nothing seems to be working. Thanks in advance.

 

[popatim]

The program/game crashes or the whole OS?

 

[seanng.alt]

The program/game crashes or the whole OS?

The whole laptop. No BSOD or visible errors, just shuts down and restarts.

 

[popatim]

Ok, I'm moving this to Laptop Technical Support for them to assist.
Thank you.