Re: System not turning on
Sounds like the case switch isn't connected properly. You could short the power on jumpers manually to bypass the case switch. If that doesn't work, you can test the PSU by removing the motherboard cable and manually shorting pin 14 and 15/16/17: http://www.techpowerup.com/articles/other/22 - that'll just turn the PSU on proper so you can check the fan spins etc.
Re: System not turning on
Ok, took it out and its working now.
The problem was the graphics card 2x6 pins. One of the 6 pin was reversed eek.
It was causing the psu not to turn on.