Upgraded Dell 435t/9000 PSU CRASH!!!

Hello,

I'm updating a computer for my boss. He has the Studio XPS 435t/9000 and wanted a better video card and PSU and CPU cooler.

I removed the mobo, attached the new cooler, new video card and attached the new PSU, Cooler Master Extreme 700w, modular.

....and nothing happens. No lights or fan movement, the on button doesn't even light up.

I took the PSU to the store and they ran it through a capacitor or whatever and the fan moved and it was fine.

Really need help as its my bosses machine!!!