hmm i think i broke something (power supply)

my sister has a fairly old computer she uses it for mainly basic stuff for school you know typing papers. well one day she says it "broke" so she brought it here to see if i could fix it, i plugged it in and turned it on to see what would happen,

well first i smelled a funny smell then i noticed smoking coming out of the back (the power supply fan) and i even saw a little light in the back inside it, i think it was sparking or on fire or something, so used my god givin instincts i shut it off and it stopped smoking/being lit on fire whatever.

so im thinking the problem the computer wouldnt boot was becasue the power supply was bad right? so i picked up a new one (the old one was a 110V this one i got was a 115V, only difference) i took out the old one and put this one in

i turned on all on, and.... nothing happens. i didn't touch anything in the computer except for the power supply wires, so im thinking the old power supply broke the motherboard or something or i plugged in this new one wrong

is there something else your suppose to do to plug in a powersupply that i missed? is it most likely the motherboard is trashed? how can i figure this out im totally clueless

If the power supply has an on/off switch, make sure it is set correctly.

Depending on what motherboard you have, there could be two spots where the power supply plugs in to the motherboard. If you have two such spots, make sure they are both plugged in.