Thaks very much for replies!
I took it back to the store this tuesday.
We had to start it up, for them to belive that there was something wrong with it. After around 15 minutes the "clack" noise started again.
Turning the computer upside down, we could observe that some wiring caused the computers fan, to halt, resulting in the extreme heat to the computer and subsequent turnoff.
They then took it back!
As it was their last computer of this model, I went home with a HP with almost the same specs.
So in some way, problem solved!