Computer Won't Powerup

[Guarding]

I recently bought a new motherboard - GA-K8NS along with a 400watt powersupply. The RAM is compatible and the CPU is an Athlon 64 3000+.

The first time I tried to power it up the thing wouldn't even start so I removed everything including the HDs. I then made sure the 12 pin mains power supply to the motherboard was working and when I pressed it down the power worked so I thought it may of been down to the connection however when I tried to power it up using the power switch it wouldn't work. I then removed the switch plug thinking it was down to the switch and shorted the power switch using a screwdriver, this worked and the thing powered up but due to there being no GFX card there was no way of seeing output to the monitor so I shut it down by flicking the switch on the PSU.

I'm not sure if this damaged it or not because now it won't work at all. So my question is; what's not working?

I have another PSU to test it with however the other PSU doesn't have the 12V (4 pin) powersupply which the processor needs.

Any help would be greatly appreciated.

 

[talldude123]

I think there is too much power for your 400W PSU.

 

[Biohazard_2.0]

First of all do not start the computer or attempt to, when you first buy a new motherboard it comes with these brass or plastic things that crew into your case, then you sit your motherboard ontop of those and then screw in your motherboard, if you do not do this you can risk frying your board or ever your processor. The reason for this is because all the metal on the botom of your board touches your Alluminum case and causes a shortage. Either that or I must ask you, are you using an AT or ATX power supply?