The BIOS password is an extremely strong password that locks out the hardware and renders the laptop completely unusable. Only with the password can you access the operating system.
A Windows, Linux or Mac password only prevents access to the operating system. It doesn't prevent you from booting other operating systems, erasing your data, or using a rescue CD to access your files.
Your computer's BIOS provides the ability to set lower-level passwords. These passwords help prevent your computer from starting up, booting from removable devices, and changing BIOS settings without your permission.
BIOS passwords are especially good for public or workplace computers. They help prevent alternate operating systems from booting on removable devices and from installing another operating system instead of the computer's current operating system.
Warning: Make sure you remember the passwords you set. It is possible to reset the BIOS password on a desktop PC that can be opened easily enough, but this process may be much more difficult on a laptop that cannot be opened.
Let's assume you've followed good security practices and set up a password for your Windows user account. When the computer starts up, someone will have to enter their Windows user account password to use it or access files, right? It's not for sure.
An attacker could insert a removable device such as a USB drive, CD or DVD containing an alternative operating system. It could start the computer from that device and access a Linux desktop: if your files are not encrypted, it would have access to your files.
So let's see how to set a password in the BIOS:
On computers prior to Windows 8, it is necessary to restart the computer and press the appropriate key during the boot process to display the BIOS settings screen. This key varies from computer to computer, but is often F2, Del, Esc, F1, or F10. If you need help, consult your computer's documentation or Google the model number and "BIOS key" for more information;
In the BIOS settings screen, locate the password option and configure the required settings. You can set different passwords, such as one that allows the computer to start and one that controls access to the BIOS settings;
You should also visit the Boot Order section and make sure the boot order is locked to prevent booting from removable devices without user permission.
On post-Windows 8 computers, you will need to access the firmware settings screen through the boot options;
On Mac computers, restart your Mac, hold Command+R to enter Recovery Mode, and click Utilities > Firmware Password to set a firmware password.