Resetting the CMOS
Method 1: Removing the CMOS battery
The CMOS battery is present in all laptops and desktops, and is the fail-safe option for most products.
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Unplug PSU power cable from wall, this ensures no power is going to the PC. If on laptop, disconnect the battery from the motherboard as well.
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Remove CMOS battery. This is a small ‘watch battery’ in your motherboard (see below).
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Press and hold PC power button for 30 seconds, this clears out any remaining charge in your PC.
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Reinsert the CMOS battery, reconnect power and try starting the machine.
Method 2: Using the CMOS Clear pins
The CMOS Clear pins are present on many desktop and even some laptop motherboards. If you can locate the CMOS clear pins (Note: Different motherboards label the CMOS clear pins differently, ASUS labels it as CLRTC, Gigabyte labels it CMOS_CLEAR, etc.)
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Unplug PSU power cable from wall, this ensures no power is going to the PC. If on laptop, disconnect the battery from the motherboard as well.
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Locate and identify the CMOS clear pins. Note that it may differ in name from manufacturer to manufacturer of the motherboard.
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Using a screwdriver, short the two pins by inserting the screwdriver between the two pins (see below).
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Hold the screwdriver in place four roughly 20-30 seconds. Press the power button multiple times while holding the screwdriver in place. Once the time expires, remove the screwdriver, reconnect power, and try restarting the machine.