Alien x51 R2 keeps crashing

Hi guys I'm writing this post with my experience with the Alienware x51 R2 and so far and am not happy with it.

               I've bought the alienware 2 weeks ago and it's been giving nothing but problems. The system wouldn't even turn off the on the very first day and I had to force to turn it off by holding the power button. The system was also laggy and quite slow at responding to simple task like opening up firefox, folder or programs. 1 week later down the road, now my alienware won't even start up.As soon as I turn it on not even pass the logging on screen it restarts and makes a loud fan noise. Sometimes the noise can last a few seconds or even longer. I've rung and spoked to the Dell Tech support he checked what was wrong with my alienware and apparently told me that the nvidia graphics card is what causing the computer to restart and suggested me to update the driver. I did, went to the website and updated the latest drivier for Nvidia 760 GTX. Everything went fine thay day. However, next day woke up did the same thing, computer keeps restarting and now it is giving me a message "please power down and connect the pcie power cable" .

               Uhhh seriously this alienware is giving me a headache, for a system that I've invested $1700 I've expected something far superior. I feel like I have wasted $1700. Oh and btw I did run a diagnostic to check all the hardware is running fine and apparently everything is running fine, although I feel like it isn't. I really think there is a hardware issue.

               Can someone help me out here and tell me what is wrong with the system?