Ideapad Y570 shuts down after only a few minutes of playing games?

I have an Ideapad Y570, with fairly decent components such as an i7 processor, 8gb RAM, and an Nvidia GT 550m GPU. I hadn't used it to do anything intensive such as playing games in about a year, but it used to be able to run things effortlessly. However, now it shuts down after only a few minutes of playing things that aren't even demanding such as League of Legends at the lowest settings. I've already updated the driver, made sure the fans got plenty of airflow, and turned down the GPU settings to ease as much burden as possible. The computer shuts down literally every time I try to play something. I don't know what is wrong, and would greatly appreciate any help I can receive. I am glad to answer any clarifying questions you may have.

 

It is probably just overheating, I'd reapply the thermal paste.

 

First, check your temps. If overheating is not the problem, then try using event viewer and see if you can diagnose the problem. If you still can't find the problem, re-install windows.