Resetting from Within BIOS, Removing the CMOS Battery, Resetting the Jumper
this app will teach you how to reset your Windows computer's BIOS (short for Basic Input/Output Settings) to factory settings. You can do this on most computers from the BIOS page; however, if you're locked out of your computer's BIOS, you'll need to reset the BIOS by opening your computer's housing and removing the CMOS battery from the motherboard, or--in the case of desktops--resetting the jumper switch on the motherboard.
In some cases, opening your computer's housing will void your warranty, and you run a significant risk of permanently damaging your computer while doing so. If you can't access your BIOS, your best course of action is to take the computer into a tech department instead of doing it yourself.