System will not boot?

Hello
I have IBM desktop motherboard 225782U from yestarday I have problem of booting. It will not turn on until i unplug the power cable then plug back then it can be boot. it turn off normal all the led lights are off, but the cpu fan is still runing then when i push the power bottm it will not start nither the cpu fan will stop. Then I have to unplug the power cable that time cpu fan stop and iam able to turn it on from sart power bottm. I have reset the cmos battry not helped. Reset ram and HDD. I dont know if this will be the motherboard or power supply. Can somone help me please?

Thanks