System will not turn on

hey, i was messing around with the LED's in my system, and it crossed a wire, and now the system wont turn on at all. if i press the power button, nothing happens. if u unplug it, and wait a while, then plug it back in, the hard disks go, and the fans/lights are on, but i dont get any screen on the monitor. it acts like its not hooked up. so i tried 2 diff monitors, neither worked. then i made sure all the electrical connections were right in the computer, and i finally tried replacing the power supply box thing, and it still will not turn on.