Some motherboards will try to recover automatically from nonbootable BIOS settings. Some do not. Those generally need to have the BIOS settings cleared.
I have been experimenting with OCing my CPU, I never did anything crazy, I was being rather conservative. The highest I got it up to was 3.5 Ghz at normal voltages, highest I went was 4.75v
Did you have the CPU voltage set to 4.75 volts or is that a typo?
4.75 volts on the CPU for any length of time will fry a CPU.