Yes, I'm using HDMI port because it has this board.
I wont to itemize that actualy i haven't mouse and keyboard. But I think that this isn't a problem for black screen right?
According to the specs of that system the only video connector is has is VGA.
Start at the beginning, has this system ever worked for you? What have you tried already? It turns on, any error beeps? Try different RAM? Just because it turns on does not mean the power supply is good. Could be a bad motherboard also. Remove the RAM, does the system give you error beeps?