pressing the "on/off" switch of my computer.
Situation: last night, while installing a new web chatting software on the other computer in my home, all of a sudden the screen turned completely black, with "no signal" flashing off. The box seems to be completely shut down at once. While attempting to restart the computer by pressing the switch on the box, there was absolutely no response from the system. i.e., even the fan of the PSU does not run.
The first reaction from my mind is the PSU is dead. I happen to have a brand new PSU at hand and thus I replaced the old PSU with this new one. Unfortunately there is still no reaction at all.
Question: what kind of damage on which part of the system can cause such problem? And how should I fix them? Thank you very much!
Background: it is an old P4 1.8G computer on Samsung P4S5A motherboard. The blackout screen incidence is not the first time to happen. It usually happens while attempting to load network visual applications with other work. The previous incidence did not prevent a restart, however.
Thank you very much for your help!