HELP: power surge in "CPU_OPT"

So i accidently inserted my 3-pin CPU fan into the wrong place in the CPU_OPT Port,
As the CPU Fan cable has 3 pins, they were inserted in the CPU_OPT falsly causing the computer to immediatly shut down ,
And when i try powering it on again, it powers for exactly 0.4 Second then shuts down again..
I require help
I checked the RAM and VGA , cleared cache but nothing seems to work even when i diconnect everything but the CPU.

If I'm reading this post correctly you inserted the 3-pin fan backwards? If so then you may have sent +12v down the fan speed sense line. This is obviously bad and why the ports have tabs to prevent this from happening. Try switching the power supply on and off several times. If this doesn't fix the problem you may have shorted out your motherboard, PSU, or both.

try clearing the cmos as well

Well, if it was .6 seconds, I'd have a different answer. So since its .4 seconds, go with what they say.

Being serious, that's not good. I would leave the battery out, unplugged, etc overnight, plug it all back in and see what happens. They try with another known good PSU (or do that first) if you have one handy...