It sounds like you have a BIOS password in force. Gaining access to your computer's motherboard Basic Input/Output System (BIOS) varies depending on which brand of motherboard you have, but the procedure is generally the same. When you power up, look for a message, usually white text on a black background, which says "Press Del to Enter Setup," or it might say "Press F2 to Enter Setup" or if your machine is a Dell, you have to hold down the Control and Alt keys and press Return. You must do this at just the right moment and you haven't got long to do it, it's quick! Once inside the BIOS, look for the User Password Entry and follow the on-screen instructions, you have to enter the old Password first then enter a new one, usually twice to confirm it. Important: be careful and don't change any other settings, this is the fundamental soul of your computer! If you set a Supervisor Password you would have to enter it to actually enter the BIOS, so this isn't the one you want to change as I understand your post. Regards
Can any genius here to show me how to change the power on password (when there is alredy one in place which I know)?