Turn the power off. Power down the PSU. Remove the CMOS battery. Usually a couple minutes will do, but it can take up to 10 or 15. So, easier to just remove the battery for 15 mins. Once your waiting period is up, replace the battery, power up the PSU and turn the rig on. It should boot up with default settings.
Never....ever, ever, ever, use the "auto-overclocking" crap. It's horrid...