Troubleshooting: Powers on for milliseconds and shuts off while power still flows

This build has had trouble for a long while now, going through 3 motherboards, a new set of RAM, and 2 new HDDs in attempt to fix the ongoing problems. The original problem with the RAM was fixed with a simple swap and the computer was able to function without problems for 2 -3 months. Then, after a long period of functioning fine, the computer would crash loading into programs. In order to alleviate the frequent crashes, we attempted to re-installed windows dozens of times which always failed. Following many attempts we diagnosed the problem as a HDD failure and replaced the hard drive. The problem still continued. It was then diagnosed as a problem with the motherboard and we bought a new one of the same make and model. That proceeded not to work. We then bought a new brand motherboard with a completely different problem. The computer now turns on for a millisecond then immediately turns off while the keyboard LEDs stay on.

CPU - AMD FX - 6300

Motherboard - (1st) MSI 970A-G43

 - (2nd) MSI 970-G43  

 - (3rd) Gigabyte 78LMT-USB3 

RAM - Crucial Ballistic Sport 2 x 4GBs

HDD - Western Digital Blue 1 TB

Power Supply - Corsair CX430M

Graphics Card - Galaxy NVidia 550ti

well 430W should be more then enough normaly.

there seem something wrong with the system. could be a fault psu offcourse, but also something diffrent like cpu or ram. or even mobo again...