Black / Blank Screen. Please read carefully.

I'm using HP Probook 4520s with i3 330M, 8GB DDRIII and Mobility Radeon 530v (43xx / 45xx series).

A few days ago I installed Windows 8 RTM Enterprise, all the latest updates, drivers etc. I'm mainly using my laptop for graphics (Adobe), web and networking. Windows 8 was working fine for a week or so. A few days ago it was hanging on me on shutdowns, longer than the usual, but still managed to shut down properly.

Last night I tried to restart my PC, and it hanged on "Restarting". I was forced to shut it down by holding the power button. I waited for a few seconds and turned it on again but the screen was completely black. No light at all. I saw that the HDD was working, I did a quick network scan, and it was connected, so my guess was that it booted properly. I turned it of a few times but the screen was still black, no bios, post etc.

I left the laptop to cool off for 15 - 20 minutes, and after turning it on everything was ok. No errors, VGA was working properly, I started some games, everything was ok. CPU temp was ~ 40 - 45 celsius on idle, and VGA was ~ 55 - 65 celsius idle.

This morning the same happened again. I'm trying many times now, trying to hard reset via the power button, restarted many times, and the screen is dead. No bleeps, system is booting properly and working. I've connected an external monitor but it says no signal.

My question is. Could it be that the graphic card is dead? If so, how it managed to turn on last night after a black out like this? Is this something related with Windows 8? I took of the ram memory out of the slots and swapped their places, I even took off the HDD. I've tried booting again and again and again, but I think I'm completely doomed!

Please advise,
Thanks.