Power supply trouble

[V3n0m]

When I plug in the the powercord the computers atuomaticlly start running without me touching the power
button in anyway.
I also cannot shut the down by the button either, it has to be manually unplugged.
When I say the computers are running I dont mean booting up I mean they have the appearence of running with no output to the screen.
Anybody have any suggestions on this?

[Mr.Paul]

it could be that the pins are off, like if you have a 20 pin connector and a 24 pin on your mother board it might not work, or other way around, like a 24 pin connector and 20 attached to your motherboard

[V3n0m]

I checked and it is not the problem. This computer is not a new one, it did work but dosnt anymore.