Let me guess. When you switch power on you get the black screen... Mine's been doing that for ages (easy to bypass). Leave everything turned on and just unplug it (out of electricity). Then Plug it in and it will work.
I actually made another switch (before the Power Supply), so the computer is always on, I just cut the power to it. Worked like that for over 10 years now (still does). I think something is wrong either with the main switch (between the joystick ports) or with the fuse (on the power supply unit).
Hope that helps!
k:
@Niles: What hitsounds???