Do you have a speaker plugged into the motherboard - beeps will tell you what wrong.
Also, start out as minimal as possible. Take everything out except the memory cpu and video card, no HDD nothing and see if it boots.
Reseat the memory, take out the screws holding the m/b down. Just get it as basic as you can then put things back one by one
Is there any metal touching the underside of the motherboard? A short somewhere will stop it booting too.
Its unlikely you have killed it but possible, static can kill components but I doubt it, probly a short somewhere
I've been in the situation you are in dozens of times, annoying but theres usually a solution before too long. only ONCE have I killed a board
