i think my M17xR2 Just Died. help anyone

So i have a M17xR2 with the following specs:

920xm
Single 5870m
16gb Ram
256GB SSD

was playing Diablo 3 and realized the GPU Temps were through the roof. im talking around 115 Degrees. so my laptop just shutoff and when trying to power it back up nothing would happen. no lights & no fans. after about 20 minutes of letting it cool down in the off position and removing the power adapter, power supply, and CMOS battery and also holding the power button down to drain it, i tried again to power it up and to my surprise it booted and loaded into windows, but only for a short period of time and then shut off again. i then let it cool down for a another 20 minutes and same thing no lights no fans nothing, just a dead laptop.

I have a spare m15x lying around in which i tested the 5870m in and low and behold the GPU is trashed, but boots with lots of graphical artifacts on the screen. i also tested the cpu in the m15x and its working just fine. so i know the GPU and CPU are still both good and will boot the laptop.

I then put everything back in the M17x and tried again and this time i get the keyboard lights, alienware logo on the screen lit, all the lights are on but i get a black screen. i tried a working 7970m in the gpu slot and still black screen.

I've taken this thing apart at least 10 times in the pass 3 days and cannot find out whats wrong. so its current state is that the laptop powers on with all the lights, the gpu fan goes to high for a few seconds and then stops. I do not get any blinking caps/scroll/num lights though even though i boot the laptop up with a GPU or without a GPU.

any help is appreciated. I'm thinking the mainboard is dead since i put a working CPU and GPU in with no luck.

Thanks in advance.

 

Seems like the motherboard could be the issue.