Hp 8560w booting into black screen, seems to be booting without display

Question

Hi,
Ive got this elitebook 8650w from a friend who asked me to help him try to get it to run.
First thing noticable that something was wrong with this machine  is when it started shutting down/rebooting randomly,  i suspected overheating since it hadnt been cleaned and doing these shutdowns while it was running 3d games.
I told my friend he had to get it cleaned or it could sustain damage.
The next day the system started to reboot right after it completed windows logon, getting into a loop.
I suspected the temprature failsafe was doing this, because after the system did one cold start,it would boot to windows,reboot on its own and then wouldnt get through the boot process alltogether and just showed a black screen with the cooling fan running at top speed, capslock blinking.
It wasnt even showing the hp bios startup screen anymore.
I tried hooking up a monitor to the external vga,  but the monitor goes into standy and remains black.
I know it did boot onto windows eventhough it was showing a blackscreen because i could type in the logon password, wait a bit and then shutdown the system with pressing alt-f4, enter.
clearly the system boots but just the display isnt working. but it isnt giving off any beeps or showing anything on boot.
So i took out the cooling parts and cleaned it to redo the thermal paste.
the job had previously  been done by hp, and turned out to be done very very poorly,   half the GPU didnt even have thermal paste onit, a big airbubble prevented contact for more then 2/4th of the gpu surface.
i feared a burnout,  but the surface didnt show discoloration and it had been working like this since he got it.
Eventhough it was a poor job done, it didnt seem to be burnt and the temperature failsafe just saved it from burning out.
After thouroughly cleaning the big blobs of paste hp put there most of it ending up next to the gpu and cpu instead of onit,blobs big enough to cover atleast 4 of the same type gpu's/cpu's
I redid the thermal paste using arctic silver number 5, the way it should be done and then reinstalled the blocks and heatpipes.
It all went smoothly into place and i reassembled the parts taken off the laptop.
Confident i rebooted, nothing changed and the problem persisted, it seems to be booting, but the screen doesnt display a thing, and stays completely black.
Shining a light onto the screen doesnt reveal any unlit graphics due to a broken backlight or anything.
Since it went through this loop often and me and my friend have been pressing keys to see if it would boot into a bios screen or anything i suspected the bios might have gotten screwed up, so i decided to try and restore default bios.
But how to do that without a screen?   i tried locating a bios jumper to do this  but didnt find any.
Then i found a text the hp forom saying i could force factory setting by pressing f10  repeatedly  5x times during startup, then f5  for default and then f10 to safe and exit,enter.
I did try that a couple of times,  but the machine doesnt reboot as it should when you safe an exit bios, s i dont even know if i get into bios in reality.
Now ive come across a few known problems with this machine in my forumcrawling.
2 problems wich results in the same behaviour are : 1 a faulty mobo and 2 a faulty board for the webcam behind the top of the display somehow preventing the screen to work properly.
So , dear hp support -  are there any known problems and sulotions to them other then, drain power and boot again?
If this machine did appear on the market with some of em having a faulty mobo, like some mssges say, why is that not on the  official forum, and could i be dealing with such a machine,  how do i find out?
If im dealing with a broken display,  could that have been caused by a videocard overheating?
You can help me by telling me:
-Can i force bios default without having an active screen? if so,  how?  just pulling the battery and draining power didnt change a thing.
-Can i find out if GPU is broken  (the system does seem to boot in the dark on a cold start)
-Can i find out if the display is broken by blinking messages or someting?
-Are there other known problems with this machine that give these failures as a result?
Can it be theres a broken inverter for the backlight? i geuss not, the vga port would be working then.
hopefull for an answer,
A friend's computer fixer.

Answer 1

I brought it into the Apple Store and I was completely denied of the 8600m GT recall. I am not paying $800 for a **** logic board replacement! Seriously, what the ****!?
I find this problem just as bad as the 8600m GT failures because this isn't the only forum I've been too that have people complaining about the same thing.
I don't know what to do anymore. Money doesn't grow on trees and I need a working laptop for school.
If anyone has any other suggestions please don't hesitate to let us know here.
Good luck to the rest of you!