You seem to be going only be video, I would check for sound first to see if everything is hooked up right and you have a good motherboard to start with.
When the system first starts up there will be an intro jingle and then if the intro music is enabled for your game it will start playing. If you can hear any of that, then you know it is something wrong with the video cabling or the monitor.
Also, check that you are getting +5V from the power supply. It doesn't matter if you are using the new or the old PSU, but you may need to tweak it to to +5. There is usually a little metal knob on side of the PSU for this. You should still see some signs of life even with the voltage off, but worth checking.