PC sometimes doesn't boot even with power.

Basically I just built simple system that is enough to run couple of games for some kinds. The whole system works fine when it turns on. Problem is it doesn't always start, it starts with all the lights fan spinning gpu working but no post or beep. I have to switch the PSU switch off and on try if it turns on and try again until it turns again. Once it starts I can switch it on again without any problem although there are times that the display dies randomly but PC still running and the next day I have to repeat the same steps or open the whole PC then resit everything just to get it working. I have tested all the parts on a separate motherboard but all components seam to work properly.
its an old spec build but good enough for me not to cry on budget specially when I have to buy most of the games for it.

its just a G41 motherboard
core 2 quad Q9300 2,5Ghz
4Gb ram
GTX 560 OC edition
FSP 500-60APN 550watts PSU

I built similar unit allot of times and I go for this build because it can handle most game titles to date but I'm not sure what cause the issue this time. Any hint?
Reply to Jerahya
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  1. Best answer
    Your power supply appears to be a split rail design, and each 12V+ only supplies 18 amps:

    The split rails are not additive, each only provides 18 amps.

    Most literature I've seen regarding the GTX 560 says 500W and 30 amps on the 12v+. You need a single rail that provides that.
    Reply to cherry blossoms
  2. Well I should have made more research before choosing the PSU. At least I learn something. Thanks!
    Is it possible to fix this issue by using a 2 molex to 6 pin?
    Reply to Jerahya
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