there are two ways to force the Bios/CMOS to be reset to its default values:
#1: mechanically, by removing all power to the Bios/CMOS forcing it to reset itself to its stored defaults.
#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.
try #1 first, and then move on to #2 if necessary.