CMOS (Complementary metal oxide semiconductor) refers to the battery-powered, semi-conductor chip located on an HP computer's motherboard. It is where the BIOS stores important information regarding the PC's system configuration. CMOS is required for an HP laptop and its hardware to run stably.
Sometimes, however, it is necessary to clear CMOS, such as if you lose your BIOS password or your BIOS is corrupted. Clearing CMOS on HP laptops varies depending upon the model, but for a lot of laptops, the process simply requires removing the battery for a short period of time.
Power down your HP laptop. Remove the AC adapter and any other peripheral devices. Turn over the computer so that the bottom side is facing up.
Ground yourself, either by touching a piece of unpainted metal or by wearing an anti-static wrist-strap.
Locate the battery. This will vary depending on your laptop's model, but it is usually located on the back, near the rear of the laptop. Review your laptop's documentation to find the battery, if needed. Many newer models require that you remove the battery by releasing or holding down one or two latches, then gently pulling the battery out. Some models may instead require that you unscrew the battery from its compartment.
Leave the battery out of the compartment for at least 30 minutes. Do not attempt to turn on the computer and do not touch the battery within that time. Some HP laptops may require you leave out the battery longer to clear CMOS, others might take only 10 to 15 minutes to reset.
Ground yourself, then put the battery back into the HP laptop. Snap the battery latch into place or screw the cover back on, if necessary.
If the CMOS is still not cleared after removing the battery, you can try to use a CMOS cleaning software.
Do not clear CMOS unless absolutely necessary, since you will lose all of your previous settings.