I recently put together a new build with an MSI Z77 MPower motherboard. Everything was plugged in and seated properly;
All standoffs in correct place, 24-pin/8-pin connected, front switches & LEDs connected correctly etc. All turned out great when I flicked the PSU switch (blue LED lit on the top left corner of the board) and looked good when I turned the power switch on. Fans spinning, video output on 770GTX working (I had a black screen prompting me to go through setup as new it said a new CPU had been detected) all was looking normal.
I installed two BitFenix Spectre fans as part of the build which come with an additional pin for its LEDs which I left unplugged when I first booted up the system. I switched the system off but foolishly plugged in the LED pin in the wrong jumper on the motherboard without turning off the power supply off. When I connected it, the system turned itself on for a brief second (as well as powering the LEDs in the fan) before switching itself off. I haven't been able to power the motherboard since and I'm worried that my error has completely killed it.
I have tested my other components (PSU, RAM etc) on another system/mobo and they work absolutely fine. I've since taken the faulty motherboard out of the case and connected just the PSU, 24-pin & 8-pin and RAM and still nothing. No LED on the motherboard, no power, nothing. I've taken out the battery too, and still nothing. Its becoming a bit of a lost cause and I'm doubting there's a home remedy to get the board working again. I don't mind shelling out for another one, I just want to get a second opinion/confirmation that there's little to no chance in bringing the board back from the dead.
Alright if that's the case then your board more than likely is dead, i say this because that connector is carried on a major power route of your motherboard and it wouldn't be hard to fry a component upon improperly shorting it out with that potential amount of power.