I have an Inspiron 600M. I plugged the power cord into the wall outlet, but when I tried to plug the cord into the computer's AC connector, I missed, and touched the serial connector. A puff of smoke came out the back, and the screen froze. I immediately turned off the computer, but when I tried to turn it on again, it wouldn't start. The green lights above the key board flicker for 2-3 seconds, then it shuts off completely again.
Can anyone tell me what's wrong with it?

I think you have blown your motherboard.