Hello,
On startup (during the tests about memory or processor)look for F1, F2 or
F10 reference to setup (if you don´t see any because of some screen with the
brand of the machine or something like that keep one key pressed until you
hear a beep, that should make the machine give an error related to the
keyboard and then you should have the option to enter setup or bios), after
entering setup look for "password protection" or something like that you
must deactivate the boot protection.