Compaq Computers
For Compaq computers, master password can be calculated using the "locked code", also know as the password hash or the disable code. How will you get this code? Simply enter wrong password in the locked computer for three (3) times and you shall see the "disable code" or "lock code" like the 5-digit code in this screen shot:
In other older or newer models, the password hash or "disable code" is composed of 10 alphanumeric characters like ACE007O31C.