Please help: Dead PC

I'm just an end-user, not a technician.



I was trying to reuse an abandoned AMD Sempron 3000+ desktop PC.

When the Power button was pressed, the PC was still off, even PSU's fan was off.



I had tried replacing the PSU with another one, replacing the system unit casing (just in case the Front Panel were damaged), but the PC was still off.



I had also tried turning on only the PSU (directly connected to the electric power source), but its fan was off too.



Is it the PSU, motherboard, or else, that is damaged and needs to be replaced? :confused:



Thanks in advance.

Please help: Dead PC