Hi *Gary*. A few points.
When you switch on the computer, do you get the POST beep from the internal speaker to confirm that the motherboard has passed it's self test?
When a computer takes a time to allow you to switch on, I first wonder what there is that can take this long, and the most likely is something cooling down. The parts that I think most likely are the processor heatsink and the power supply.
The monitor not coming on is usually caused by no signal, but if the motherboard isn't booting, there won't be any signal anyway.
If there isn't any POST beep, disconnect both hard drives and try again. The computer should still get to POST an then report that there is no Operating System.