computer powers down on boot up sequence

i received a photo zip file of windows live messenger and opened it, after
that the computer randomly powered down for a day. the next day it would not
start. i turn it on and at different intervals it turns off. it wont boot up
in safe mode. i have occasionally got it to boot into a command prompt but
that is it. it has happened on 2 computers in the house and i am at a loss.