Computer powers on, but does not load.

Hello everybody, I have a problem getting my computer to start.

When i power on the computer, there is no beep. My monitor light is orange and there is a blank black screen.

The issue before was it didn’t power on, I changed the power supply and the computer now powers, but nothing else seems to happen.

Fans works, i believe the HD is spinning, It’s a very old Athlon, i don’t know the specs. the computer was bought in 2000. the power supply is ATX supported.

Could it still be the Power supply? or the mother board (mother board has light)?