My pc only turns on when the main power is connected to the mobo.

[LeoStromeyer]

When i try and connect the 4 prong power source to the motherboard, the fans and lights quickly flash and stop spinning after about 1/4 of a turn.
When i disconnect the 4prong power cable, and only leave the larger power cable in, the pc turns on like normal and stays on, but displays no picture on the monitor and also the mouse doesnt light up?
Am i right in thinking that the processor has broken? and that the pc needs the 4prong power source to function properly?
please help,
thanks

 

[Whiffen]

You should have to have all of them plugged in. Did you miss another power connection on your mobo that gives power to the CPU?

 

[LeoStromeyer]

yes when everything is plugged, the lights only flicker shortly, but when the 4 pronged power plug isnt plugged in, the computer starts up and runs.

 

[Tmagic650]

Sounds like your trying to connect the wrong connector to the wrong spot on the motherboard and your title "My PC only turns on when the main power is connected to the motherboard"... is a bit silly. I think you left out the word "briefly" between "on" and "when" in the title