To utilize this technique, ensure that your motherboard has a dedicated Clear CMOS button or reset button on its rear or on the front panel. If it does, follow these steps:
Shut down your computer.
Unplug all cables from the back of the PC, including power.
Locate the Reset button on your motherboard’s rear or on the front panel(On my PC it’s present on the front side).
Press and hold down the button for 5-10 seconds.
Release the button and plug everything back in.
Power on your computer.
Be aware that resetting your CMOS will cause any BIOS changes you made previously to be lost, so make sure you have any necessary information backed up before performing this procedure!
For detail check How to Clear CMOS
