You could have a bad ram slot on the board (seen it before ) Try putting the one stick that you know is good and try every slot one at a time and see if one slot does not boot , You May Need another board ??
Thank you for your response.
I tried what you asked, and it seems whenever I put 1 memory module in a black slot (does not matter which module or slot) the computer gives the 3 beeps error.I guess i'll return the board for waranty.
When I took out the box of the motherboard to return it for waranty, there was a sheet of paper with it that said: "The intel core i7-800 and intel core i5-700 series requires memory to be populated in the channel A, DIMM 0 Socket". So no wonder when I use only the black DIMM slots the computer fails to boot.
Stil leaves the question if the other modules are defective or not.