Asus A8N-VM CSM (s-939) is damaged?

Hello.
i opened the case to clean my rig,
i wanted to open the cpu heatsink so i played with it a little but couldn't
get it to open.
i said "ok, have it your way" and closed the case.
i powered up my system and then nothing happened.
there is no post massage. the screen says "no signal" and the led
of the HDD is constantly on. the fans are spinning without control on max RPM.

so i got my hands dirty and this is what i tried:

*opened the case. managed to open the fu**ed up heatsink
cleaned it, applied new thermal grease, closed it in the proper manner and still the same problem.

* I decided to check things on the Power supply side so i installed other PSU - same problem.
i tried my PSU on another system - works fine. so it's not PSU.

*tried to remove and reconnect the memory dimms, one by one - still nothing happens.

*i thought maybe the case is shortening the board, i took the board out of the case and put it on a carton box then powered it up - notingggg!

*i took out the CPU 3 times and verified that it is sitting on is socket like it should - same happens.

jeez, I'm totally desperate. PLEASE HELP ME!!!

my guess is the Motherboard but it could be also the cpu (although not likely)
so how can i tell if the problem is in the cpu or motherboard for certain?
i don't have other Mobo or cpu i can try...