Originally Posted by Cressida

OK, provided you have checked all the connections shown in post #13 and provided that the CPU+Heatsink/Fan and the RAM stick(s) are installed correctly, there's only one more question I can ask and that's whether the two wires from your PC case's power switch are connected to pins #15 and #16 of the Front Panel Header on your mobo (see attached extract from your mobo manual).

Shorting those two pins momentarily should boot your system and allow you to enter the BIOS setup, even without any hard disk or optical drives attached. (You'll need a monitor and keyboard to navigate inside the BIOS obviously.)