The really obvious thing here is to make sure that the IDE leads are connected the right way around with the red stripe closest to the power plugs on the drives and inserted the right way around on the M'Board.
It's sometimes possible to plug in the IDE Lead the wrong way around on the M'Board. I would also check the Power Supply to make sure that it is actually supplying the correct voltage.
If none of that works remove everything from the M'Board and reseat it, and then remove everything except the Video Card, CPU and try to boot from there you should hear a series of beeps that are telling you that there is no memory present. Once you hear this power down and remove the mains lead and insert 1 stick of RAM and try again to see what if anything happens. If you then get a normal POST Screen plug in 1 HDD on the primary channel and try again, if this works then power down unplug and plug in the Optical Drive and try again.
If it works from there you can start shutting down and installing one bit at a time until it all together and working or fails to boot at which point you will know the problem part.
If this fails I would recommend that you fit a PCI to IDE controller card from Promise Tech as it will work without drivers and then run the Ultimate Boot CD to test the M'Board for problems.
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Col