no power to motherboard??

[AthruZ]

ok..little update.
Finally got some spare time today and thought I'd start from basics.
Took the MB out of the case, heatsink/fan off. Took the cpu out and cleaned all the thermal paste off that and the HS...layed the MB on cardboard, cpu in, HS/fan attached, ram in ddr3-1, 8 pin in, 24 pin, power button module from case plugged in, cleared CMOS..all switches on, button pushed and success!!! I have MB lights on, fan spinning...tried all 3 ram modules, all worked so a complete circuit.
Now I know there is a long way to go until I can call it a working system but at least I have power to the motherboard now which means I can narrow down the problem. I am leaning towards my case shorting out the motherboard in some way??
Seems my PSU is ok after all...I'm getting a new shiny one delivered tommorow anyway (doh!!).
I think I'll keep it as it is modular and I think I need a new one anyway but just thought I'd post this progress up for others having a similar problem.

[AthruZ]

just another quick update...installed everything in the case (testing after each thing was added). Booted from cdrom, it is currently installing windows 7
I suspected it was a screw on the far top left of my case that caused the problems so I didn't put a screw in that one and it powered up.
So if people have a suspected dead MB on installation check the seating of it in the case...might save you a lot of RMA headaches.
Thanks for everyone's help.