Power supply died all of the sudden and I had to replace it. I have assembled everything with new power supply, powered on computer, but nothing happened. I can hear cooler spinning, DVD drive has a light on and can be opened but that is all. Just the black screen. Is this a possible motherboard problem?
It looks to me that your motherboard is malfunction. Obviously when power supply died it took motherboard also. It is not uncommon thing that power supply failure destroys other components in computer especially if power supply died because of power surge. I am sorry, but you will have to buy new motherboard and hopefully only that.