PC Turns On and Off Repeatedly

[eamonward]

I've upgraded an older PC, at least six years, and have run into a problem. When I boot it up, while breadboarded, it powers up for maybe five seconds, then shuts down, then repeats until I turn the PSU off. The only component in the breadboard that isn't new, is the PSU, and I think it's the problem, but I want to know if there's a way to ensure this before I go out and buy a new one.

 

[alexoiu]

What new components using?

 

[j121]

do you get any beeps?