Changing the 'international "power" button' = game over for your power supply
Unless they're intelligent enough these days to realise you're feeding it the wrong voltage, even temporarily, but I don't know
Assuming you've put it back to the correct voltage, when you try to turn the machine on (power cord in, power switch on the power supply unit switched on if your unit has one - double check this one), does it do anything other than the green light on the motherboard going on and off, eg make any noise, fans start moving even though the screen is dead?