fans turn on but nothing happens

hey was wondering if any of you can help me? i have a pc that turns on perfectly all the light on the mobo turns on, gpu lights on,cpu lights on. the problem is that the pc will not turn off when powered on, nothing on the monitor shows up (monitor works been tested), no lights on keyboard or...

I have a second hand PC with some Corsair hardware already installed. I have a Corsair Obsidian 900 case, commander box, two corsair splitters and 2 x 4 Corsair 4 pin fans installed in my radiators. Commander box is connected to Asus Rampage IV Extreme motherboard and commander 1 cable goes to...