Computer won't boot

Hello,
DJ AKSHAY,

I have a computer which I am using since last 5 years. Today morning it will not boot. Power button won't do anything. There is a green light on the mother board stays on when it is connected to power supply. When I press power key, nothing happens, no fan, nothing. I have replaced the power supply and it did not make any difference. CMOS battery is dead on my computer since a while as I know it looses the time, when power goes off but I suspect it should not be issue with powering of mother board.

I removed the memory and did not here any beep sound. Also cpu does not get hot. I don't have any 4 pin 12V connector on the motherboard, is this normal in the old motherboard (A7N266-VM)?

At this point I suspect motherboard, any suggestions?