Computer not booting

[Stephan_5]

as title said, my old computer wont boot. It starts up (fans spinning, Capslock can be turned on and off), but there is no display, and it turns off after some 30 seconds. The turning off part is, I think, because I cleared the BIOS, and the MOBO does not like my CPU-fan. This I can fix, easily if I ever get display working again.

hardware (that's still in there)
Motherboard: pegatron m2n7b-la
CPU: AMD: Phenom 9550 quad-core
RAM: corsair cm2x2048-6400c5

Already tried

• 
  Switching graphics card
  removeing graphics card, trying the on-board
  testing both graphics-cards in other computer, they both work
  testing RAM (starting up with one blok at a time, and swithing places
  remove all RAM (it gave the "no-RAM beep)
  removeing everything not essential (HDD, Front panel, USB sticks ect.

Still same result.
Any ideas?
ps. sorry for bad english, it's not my mothers tongue, and I'm dyslexic

 

[cin19]

Do you just upgrade the cpu to Phenom 9550 quad-core?

 

[Menelaos1996]

Well if you have a multimeter you can check the voltage of your cmos battery or if it's new leave it as is.Um do you have any PC5300 ram available to test?You say that it is your old motherboard so what happened and it stopped posting can you remember?Can you see any leaking/Bulging capacitors.