Step 1:- Check your RAM i.e. swap it with another one & See if this works.
Step 2 :- If RAM is not the the problem, check VGA cable(connects from CPU to motherboard)
exchange it with another one.
Step 3: - If RAM & VGA cable are Ok then check your Graphics card.
Step 4 :- If all of the above are OK & still there is no display then im quite sure that the problem is with the BGA chipset
I.C. You can try getting your BGA I.C. replaced with a new one or get a new motherboard.