Recently my computer kept shutting down as soon as I would power it on. So decided to get a new PSU.
Now it doesn't shut down immideaely like before but nothing appears on the screen.
My screen has LED button that can be either green(monitor is on/displays stuff normally), orange(sleep mode/afk too long/nothing on the screen until you move the mouse) and black(off/not powered on). Well my monitor has always the orange LED on.
If I try to press the button it goes to green LED at first then straight to the orange LED.
Also my video card, back when my PC was working fine, during initial startup of the computer, for about first 3-4 seconds the computer was powered on, it would spin its fan really fast which would make whining noise and then stop and spin normally. Now my VGA spins the fan this way non-stop and there are no POST beeps.
What video card do you have? If you have one that needs a 3-pin or 4-pin power connector, make sure that is hooked up. I had this problem when I forgot to plug in the 3-pin power connector to my ATI 5770 and because of this, the graphics card did not have enough power to run the display. That may be your problem.