Shut down the computer completely
Unplug the power cable
Remove the laptop battery if it is removable
Press and hold the power button for 10 to 15 seconds
Open the case or access panel
Locate the CMOS battery on the motherboard
Note the battery orientation
Gently release the battery clip or connector
Lift the CMOS battery out carefully
If it uses a cable connector, pull the connector straight out
Wait a few minutes before reinstalling or replacing it
Reinsert the battery in the same orientation
Close the case or access panel
Reconnect power and start the computer