Hi
Your problem is your PSU is an old style that is nopt compatible with the new style motherboards. I would recommend a well known make such as Corsair, Enermax, Seasonic, Silverstone, etc of about 550W at least (depending on your system) and a single 12v power rail.
You must have the ATX connector in the top right corner of your motherboard attached to the 12v supply from the PSU in addition to the 24 pin cable. The fact that you might have a 2 x 4 pin cable makes no difference as long as they are both fitted.