You may be prompted for the BIOS password right after your machine has been powered up, before the system boots. Or you may be allowed to boot your system, but a password is required to access BIOS Setup.
1. If you cannot access the machine after it has been powered up, you can pull out the CMOS battery and insert it again. In this case all BIOS/CMOS settings will be reset and you will be able to reboot your PC and change the password.
2. If you are able to access the machine after it has been booted successfully, but need a password to enter BIOS Setup, please try some BIOS password cracking tools.
3. Please note that laptop/notebook BIOS passwords cannot be reset by shorting the CMOS battery. BIOS passwords in most laptops are stored in a special chip on the motherboard and the only way to bypass this password is to replace this laptop security chip: www.pwcrack.com.
For more information about resetting a BIOS/CMOS password please read this archived copy of article: Removing a Bios - CMOS Password