PC wont even kick

Hi
I have a P4S800 MB, P4 2.8 Ghz CPU, RADEON 9600 128MB Graphics card and 512 DDR 400 RAM.
Problem: I connect everything i can find and double check all the jumpers etc but nothing happens when try and turn it on (there is power in the MB because the MB light does come on). The fan doesn’t even start.
Any Help would be great!