resetting bios setting will not do any harm to your PC. Your mobo must have come with a instruction manual - follow that to know how to reset/clear CMOS setting.
There's a simple way to do it though - power off your system and remove the coin sized big battery from the mobo and put it back on after say a minute or two - this will reset your cmos setting.
After doing that the bios will prompt you correct a couple of bios setting - just follow the mobo manual to set them correctly.