is the i7 875K supported by your motherboard out of the box? If they recently added support for that CPU then that could be causing problems too.
If you followed the instructions on AS's website then you didn't use too much.
Did a quick check on ASUS' site and ran across this.
Core i7 875K(2.93G,L3:8M, rev.B1,) BIOS Revision Required: 1607
BIOS 1607 Info:
Description Maximus III Formula 1607 BIOS
1. Improve memory compatibility
2. Improve system stability
3. Fix 2.2T HDD size is wrong if Quick Boot option is disabled
4. Improve compatibility with some USB3.0 devices
5. Support new CPUs. Please refer to our website at: http://support.asus.com/cpusupport/cpus ... uage=en-us
File Size 1.06 (MBytes) 2010/04/08 update
Have you tried booting with the bare essentials? Meaning CPU, one stick of RAM, video card, keyboard, mouse and nothing else? If you've tried everything else pull the motherboard out of the case and set it on the box it came in. Try to start it then. If nothing is happening then there's a good chance you didn't do anything wrong and the board is DOA. I've had 2 DOA boards in my computer building endeavors and they were both ASUS. I know that doesn't make you feel any better but this was also several years ago.