Computer Fans spin for under a second

My computer started overheating and rebooting a few months back and then one day it didnt turn on. I suspected it to be the power supply (Corsair 550W VX Series PSU) Emailed them for a warranty they said put metal between the earth and another part of the mobo connector lead and see if the fan spins which it didn't. GREAT i though it's the mobo that's broken, sent it to the Netherlands and today I get a brand new PSU, computer still doesn't turn on.

Now when I turn the PC on the fans spin for under a second then off, it is not shorting as I have tried it out of the case and I can do it continously without having to reset the PSU. I have removed every non essential part leaving just GFX card,cpu, ram and HD.

I have tried removing one slot at a time, no luck. I hear no beeps.

My mobo :
Gigabyte GA-P35C-DS3R Socket 775 8 Channel Audio ATX Motherboard
CPU:
Intel Core 2 Quad Q6600 Energy Efficient 95W edition Socket 775 (2.40GHz) G0 Stepping L2 8MB Cache OEM Processor
CPU Fan:
Arctic Cooling AC-FRZ-7P Freezer 7 Pro Socket 775 Processor Cooler
GFX:
Nvidia 8800 GT 512mb
And Its not the ram I have tried 2 different types.

I hope I have been helpful.

Thanks for all your help.

Henry