I have an ASRock AM2NF6G-VSTA

Question

I have an ASRock AM2NF6G-VSTA motherboard that will not power up. I upgraded the system and powered it up and it ran fine, except I had not received the new upgrade power supply. I received and installed the new power supply and no reaction to pressing the power switch. I reinstalled the old power supply, no power up. I reset the CMOS, no power up. what do I check?