If this were an IT web site, this thread would get locked for discussing the verboten
topic of password recovery. Since it's not,....
Forcing the Bios-CMOS to be Reset to Default Values:
There are two ways to approach forcing the Bios/CMOS to be reset to its default values: Option #1: Mechanically, by removing all power to the Bios/CMOS thereby forcing it to reset itself to its stored defaults, which include no password or the default password employed by the Bios manufacturer, and Option #2: Using a program to either locate and identify the password and reveal it to you or erasing the password entirely. These are referred to as password by-pass utilities or cracks. Let's look at Option #1 first, and then move on to Option #2 if necessary.
Option #1: Mechanically Removing the Password
Most motherboards manufactured over the last decade or more use a battery to sustain the dynamic Bios/CMOS settings for the motherboards PROM chip. These dynamic settings are those manually set by either the computers manufacturer or you, the user. There are two ways to erase these dynamic settings, by either resetting a jumper on the motherboard itself (referred to as a "clear CMOS" jumper), or by physically remove the power from the computer (disconnecting the power plug) and then removing a battery (used to maintain power to the PROM chip that contains the Bios/CMOS information) from the motherboard.
Some, but not all, motherboard manufacturers provide a set of three jumpers on their motherboards that provide you with the ability to clear the Bios/CMOS settings, thereby allowing them to be reset. For the most part this is used when the Bios/CMOS data becomes scrambled and you need to clear the Bios/CMOS in order to return the computer to a functional state. This same procedure, however, can be used to clear passwords from the Bios/CMOS setup. Typically a jumper will be found across pins #1 and #2 as the default position, and by shutting the computer down, unplugging the power cord and then moving the jumper so that it is across pins #2 and #3 will clear the Bios/CMOS settings.
Complete online article here