That sounds like a classic failed power supply scenario to me, which is odd since you said you just replaced it. I find myself wondering if the power supply you bought as a replacement is also, by some crazy chance, also faulty. Did you compare the power supply's output levels to the amount of power your system components are drawing? It's possible your power supply isn't rated to provide enough power to your system.
You could try stripping all the parts out of your system and reducing it down to a barebones setup. One hard drive, no optical drive, one memory board, etc. See if it boots that way. Then systematically go down the list of your components, inserting and removing them so you are always running a bare-bones system at all times. If you have multiple memory boards, insert one at a time, instead of all at once. This process of elimination will help you identify if the problem is related to a specific component.
If that produces no results as well, then I would be inclined to think your CPU is fried, or that you somehow bought a faulty power supply or motherboard. Hope you kept the receipt.
You could try stripping all the parts out of your system and reducing it down to a barebones setup. One hard drive, no optical drive, one memory board, etc. See if it boots that way. Then systematically go down the list of your components, inserting and removing them so you are always running a bare-bones system at all times. If you have multiple memory boards, insert one at a time, instead of all at once. This process of elimination will help you identify if the problem is related to a specific component.
If that produces no results as well, then I would be inclined to think your CPU is fried, or that you somehow bought a faulty power supply or motherboard. Hope you kept the receipt.