Before powering on, change the CPU multiplier settings on your board to a lower setting (actually the setting itself doesn't matter, just as long as you make some change). Then power on and the PC should boot up, albeit with an incorrect CPU speed. Shut down, change back the CPU settings, and it should be OK.
I had an identical problem with a failed BIOS update and this solved it for me.
My PC is so wonderful it makes Svol seem less than perfect