Computer burn out & not turning on

Hello guys,
I have a PC that has Windows 7 ultimate, my motherboard is D945 GCNL & my processor is Intel dual core & video card is NVIDIA 9500 GT.
I am really fond of gaming. Last night while playing the Call of Duty 7 my pc just had a blast & my pc turned off & some burning smell come out. After that I am not able to turn it on.
What is the problem?
