CMOS settings can be edited via firmware called BIOS.
The CMOS (Complementary Metal-Oxide Semiconductor) is the part of the computer where central system information such as the time and drive specifications is held. To troubleshoot CMOS, edit its settings via the preloaded firmware called BIOS (Basic Input/Output System). In cases where the system is not booting correctly, it may be necessary to edit the BIOS. If the BIOS is locked by an unknown password or if the computer is generating warnings such as "CMOS Read Error," "CMOS checksum error" or "CMOS Battery Failure," the CMOS battery needs to be replaced. In cases where input and output hardware is not working properly, it may be necessary to upgrade, or "flash," the BIOS.
Instructions
Editing the BIOS
1. Enter the BIOS. When your computer boots, it displays a message on the bottom of the screen such as "Press F2 to enter setup." Instead of "F2," the key may be F1, DEL, ESC, or F10. Press the setup button specified in the message when prompted.
2. Browse the BIOS. Navigate the menus with the arrow keys. Press enter to select items. BIOS menus differ widely based on the make and model of the computer.
3. Change the default boot drive. Use the arrow keys to select "Drive." Follow the specific directions on the screen to move the necessary drive to the top of the list. Most users prefer to boot from their hard disk first. The exception would be users who are trying to reinstall the computer's operating system or "flash" (upgrade) the BIOS.
4. Return to factory settings. Press the arrow keys to highlight "Restore Default Settings." This will fix most CMOS errors.
Replacing the CMOS Battery
5. Run the computer for 24 hours. This may recharge a seemingly faulty CMOS battery.
6. Find the CMOS battery. Open the computer and search for a coin-shaped battery. It is approximately the size of a half dollar. If you cannot find it, contact the computer's manufacturer for assistance.
7. Remove the battery. Place your fingers around the battery and pull it out. If the battery is under a clip, use one hand to pull the clip up and the other to lift the battery out.
8. Replace the battery after five minutes and restart the computer. This will resolve many possible problems. If your problem continues, remove the battery as before.
9. Bring the battery to a computer store. The information on the battery is complicated and specific. It is best to bring the actual battery to the store and allow the trained staff to locate the proper replacement battery.
10. Replace the battery with the new battery and restart the computer.
Flashing the BIOS
11. Visit the computer manufacturer's website.
12. Search the website for "BIOS Updates."
13. Download the file associated with the computer's make and model.
14. Burn the file to a CD. Insert a blank CD-R into the CD-R drive. Right click the BIOS update file and select "Burn image to CD." Click "OK" when the burn is complete.
15. Restart the computer to flash the BIOS. Press the setup button when prompted. Navigate to "Drive" with the arrow keys and press enter. Follow the instructions to set the CD-R drive (Generally the D:/ drive) as the primary boot drive. Exit "Setup." The bootable CD will load and update the BIOS. The computer will then restart with the new BIOS in place.
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