Brand new PC problem

[honkyhonk182]

Arctic Power 700W PSU
sapphire radeon 4850 graphics card
core 2 duo e8200
asus p5q pro mobo
2x2gb 6400 800mhz DDR2 Ram
Samsung 1tb hard drive

Built a new PC with my friend last night, it switched on, there was no signal on the monitor, then after about two minutes the power would automatically turn off, which suggests a Power/Over heating problem, I tried putting the Graphics card in the other PCI-E port but again the same problem...any help would be very much appreciated!
Thanks.

 

[J.B]

Try the RAM sticks individually, check all the connections, have you put the 12v CPU connector in thats a common mistake?

 

[honkyhonk182]

Thanks, I'll ask my friend to try the ram seperatley and yeah I plugged in the 4 pin 12V connector in

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The PC isn't turning on at all now