After a while my CPU runs at 100%, heats up and then my comp

I started playing a video game that was a little too much for my computer and i got crashes a few times. But then even when I didnt play the game it continued heating up and crashing. I decided to reinstall windows - same thing. Ubuntu... same thing. I took a look at the cpu and temperature on ubuntu and found that once the CPU reaches 100% it stays there. But at that point the computer is pretty much useles because I get about 1 frame every 5 seconds. Even when I have no programs running or anything. With the processor running on 100% it gets hot and at the magical 105°C it turns off. I think thats a good sign as 105°C is the critical temperature.

I have asked around a little and had a lot of people tell me that my Cooling system is broken and i need to get it fixed. But this is just curing the sypmtom of 100% cpu usage, not the cause. So what could the cause be? A broken CPU? It works perfectly untill the 100% is reached. When i first reinstalled Windows I had all drivers up to date and on ubuntu it crashed before I can get the drivers installed/wont let me install the GPU drivers.

My computer is the Samsung RF510-S01 Notebook. http://www.samsung.com/us/computer/pcs/NP-RF510-S01US-features

Thanks for your tipps.