Surprisingly I have the same exact problem, just few days ago I turn on the computer and the power button will light up and does nothing.
I unplug the power cord for few minutes, and try it again and it works fine.
Today I finally smelled something fried.. I took it apart to see exactly what's going on and I found an insane amount of dust which I cleaned.
Plugged it in again to see if it'll work, now the power button lights won't come on and I do see the
CPU green light on which means there is connection but overall the computer is dead.
I'm guessing it's the power unit and it costs a bit for how old this computer is.
I'm trying to find a power supply for cheaper.
Now here is the question, do any power units work with my PC? or when it comes down to it, each PC has its own power unit that cannot be mixed or matched with others?
thanks in advance.