So you get into BIOS.
You can press F5 and enter.
Then when you press F10 it fails.
Remove your SLi graphic cards. Take one card out and only boot with one for now. Maybe your PSU is not happy.
Change your BIOS - use the switch on the left hand side of the motherboard to change BIOS chips. You will see the orange light jump from one place to another place about 3 cm's apart.
Once you have done that. Do the steps I posted
Lets take this in small steps.
Power your system completely down.
Press the clear CMOS button at the back of the board, In/Out panel.
Del to enter BIOS, or follow the prompt if your system has failed an overclock.
Once in BIOS F5 and enter.
F10 and enter.
You are now in default settings.
Does your system boot into OS