Need wiring diagram for ms-7142 motherboard... fixing a friend's computer, but they unplugged the wires that run to the front... therefore the power and LEDs don't work...

The connector bus where the front wire connections go, is usually marked. It's usually two rows of pins sticking up. You should be able to determine where the power wires connect. One pin will say PWR. The second pin you need is either next to, or across from that pin. The LED pins are labled too. Keep in mind that LED's have polarity. That is, a diode [light emitting DIODE- LED] only works one way. It's a one way "Valve" for electricity. So if you determine which two pins are for the power light and you connect them, it still may not work. Just reverse the two wires to the two pins and it should work.
I can't imagine that the MSI web site doesn't have the pinout for this board. It would be worth a look if you're not sure of what I'm saying here.

Go to MSI's website and download the board's manual.