ATX connector not compatible with power supply

I bought an assembled computer system today, I have an Intel chipset motherboard, 500GB hard disk, Intel dual core processor, Sony DVD writer and Samsung SyncMaster B1930 monitor. After all the system was assembled properly, I pressed the power button of the cpu, the computer did not turn on. It is annoying me very much that on the very first day my system turned out with some issues. Please suggest me something, so that I can try something myself before the technician comes and checks the system.

Yes it is very frustrating if such things happen, but it is the first day of your computer and I can understand your mental status. But I think you should be calm and patient now. I really appreciate that your technical knowledge and you applied it in assembling the system. But I think you should wait for the technician to come and check because some internal components in the system are very delicate and in anxiety if you mishandle any of them , it may cost you more to your money and your frustration.

Well I think there is a chance that the power cable of the power supply and the motherboard are not compatible to each other. It happens in ATX connectors and power supplies. Older ATX cables had 20 wires in the female connector and motherboard had 20 male pins. A newer versions of ATX cables and power supply were introduced with 24 wires and 24 female pins respectively in the motherboard, 4 wires were added for extra power . You can plug the 20pin ATX cable into the 24 pin mother board but you cannot fit 24 pinned cable into a 20 pin motherboard.

A mother board needs to be connected with a 12 volts power cable . These 12 volts power cable are of 2 types. There is pin4 12volt cable and a 8 pin 12volt cable called a EPS12V cable. Certainly there would be no issue if there is a 4 pin cable and 4 female pin connector or 8 pin cable and 8 pin connector in the motherboard. And two 4 pinned cables cables can fit in 8 pin connector. But the problem arises when there is a 8 pin cable and two 4 pin connectors.