How to Clear the CMOS of Laptop or Desktop Computers
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How to Clear the CMOS of Laptop or Desktop Computers

Three steps on how to clear the CMOS to resolve windows computers booting problems.

There are times that you need to clear the CMOS, or the complementary metal-oxide semiconductor of your laptop or desktop PC to resolve booting problems in windows computers. This option is desirable if your attempt to solve booting problem using the safe mode function did not work.

There are several reasons why your computer will not boot up. These problems include those arising from a blank screen, an incompatible video driver that you have installed, a virus that prevents you from booting up, bad sectors of your hard disk (in this instance you need to regenerate it), incompatible hardware that you just installed, and other related causes. Clearing the CMOS will be able to help you solve these problems by bringing back your laptop or desktop PC back to the original configuration or factory defaults before you installed many other applications. 

If you decide to clear the CMOS, make sure that you have your motherboard drivers, video drivers, sound drivers, among others that go with your peripheral devices like printers, and cameras. It's like using your desktop for the first time so better get ready with the different video, sound, and printer drivers as the very basic drivers to make your computer work. 

Here are steps on how to clear the CMOS of your PC.

Procedures to Clear the CMOS

There are three ways that you can clear the CMOS. You can do it by 1) accessing the Basic Input-Output System (BIOS) setup residing in your motherboard, 2) removing the CMOS battery, or 3) manually by finding the CMOS clear or the CMOS jumper pins.

1. Accessing the Basic Input-Output System or BIOS

Gain access to the BIOS setup utility to "Reset BIOS Settings" to their factory default settings. The menu option in the BIOS differs between motherboard models but you should easily find phrases related to resetting the BIOS. For example, you might find, "reset to default", "clear BIOS", load setup defaults, among others. These options can be found under usually at the far side of the menu options or the bottom.

Here is the procedure:

1. Switch on your laptop or desktop PC or restart if you are using it.

2. Wait for it to start up then when you see a blank screen, watch for command lines (it should be displayed) that say which key in the front row of your keyboard should be pressed. Some computers can be accessed using the F2, Delete, or just any key on your keyboard. Once you press on the key, the computer may ask you again to press another key to enter the BIOS setup. Tap the key continuously (but not too much and too hard) until the BIOS setup utility is displayed. If you have overdone tapping the keys, your computer will return an error. You need to do it again.

3. Find and load the BIOS defaults.

2. Removing the CMOS Battery

This procedure is relatively easier than the first one. Just look for the CMOS battery in your motherboard. It looks shiny silver, rounded and flat and labeled usually with a "+" sign. Remove the CMOS battery by prying the plastic casing with a small, flat screwdriver. Mount it back again after 8 to 15 hours (this actually depends on the model, some require less time) to erase the memory store. When you boot up the computer, you will receive the message "BIOS checksum error" if you have succeeded in clearing the CMOS. The default settings are loaded once you switch power on your laptop or desktop PC.

3. Manually Clearing the CMOS

You can manually clear the CMOS by finding the CMOS jumpers (three pins) and connecting both ends of the pins with a flat screwdriver. You can usually find these jumpers near the CMOS battery or as labeled in your motherboard. Usually this is labeled JP4 or JP3. See illustration below:

© Patrick A. Regoniel

After clearing the CMOS using the screwdriver. Replace the plastic jumper to its original location and reboot your laptop or desktop computer. The computer should either display a prompt for your to load setup defaults or it will just automatically load the defaults and open the windows operating system.

If clearing the CMOS is successful, you may now load your device drivers.

©23 April 2011 Patrick A. Regoniel How to Clear the CMOS of Laptop or Desktop Computers

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Comments (4)

This may come in handy for me, Patrick. Thanks.

Excellent tips, Patrick.

Thanks. : )

I don't know what CMOS is, your article gave me an idea about CMOS. Perhaps, I need to read all of your other articles for additional knowledge about computer hardware parts. You have demonstrated your ability to share information to us. Keep it up! Thanks, voted and shared.