OK, thanks. I'm disappointed that this can't be controlled in the BIOS, or at least with a motherboard jumper.
But I've had an idea for a hardware modification that I
think should work, but I'd really appreciate any help:
I think the source of power to the motherboard when the PC is 'Shut Down' is from the ATX 20 pin connector pin called
+5VSB.
So if I remove the lead from my PSU to this connector pin then no power will be supplied to the mothertboard when it's 'Shut Down', right?
But perhaps the motherboard needs +5V supplied to that pin whilst the motherboard is powered up?
If so, the
+5VSB pin could be connected to the adjacent
+5V pin, if the PSU can supply sufficient current?
Any help with the three questions
above would be much apreciated :-)
Here's a picture of the ATX connector:
http://upload.wikimedia.org/wikipedia/commons/a/a9/ATX_PS_signals.jpg