Computer won't boot up

[Abubakr13]

Everytime the computer is plugged into the power outlet the system starts working for a few seconds, fans spinning, and then it stops. It doesn't turn on again even after pressing the power button, I have to unplug it and wait for a few minutes to plug it again and then it starts automatically and stops. I've tried resetting the CMOS and also replaced the CMOS battery but it was of no use. I reconnected all the power cables and it still didn't work. I removed the hard drive and RAM and tried but it still wouldn't turn on. Then I removed the CPU and placed it again and applied the thermal paste and it still wouldn't work. 

[Pachuca]

3 minutes ago, Abubakr13 said:

Everytime the computer is plugged into the power outlet the system starts working for a few seconds, fans spinning, and then it stops. It doesn't turn on again even after pressing the power button, I have to unplug it and wait for a few minutes to plug it again and then it starts automatically and stops. I've tried resetting the CMOS and also replaced the CMOS battery but it was of no use. I reconnected all the power cables and it still didn't work. I removed the hard drive and RAM and tried but it still wouldn't turn on. Then I removed the CPU and placed it again and applied the thermal paste and it still wouldn't work. 

what mobo and psu do you have? does the mobo have an led light that shows the boot codes on it? 

[Pachuca]

also, can you take a video of it doing this and post it here?