From the motherboard manual: "Inadequately altering the settings may result in system's failure to boot. If this occurs, clear the CMOS values and reset the board to default values."

This would certainly be a concern if your computer was booting. Since we're at the point now where it isn't, you can safely disregard that.

I'd probably choose failsafe defaults myself.

You can also reset the CMOS like it recommends. Power the PC off, unplug it from power and peripherals, push the power button a few times to purge the capacitors. Then remove the CMOS battery from the motherboard, press the power button a few more times for good measure, reinsert the CMOS battery, plug in power and peripherals, and boot the PC.

Best of luck!