If you set the password in the system BIOS, you will have to CLR_CMOS (clear and re-set the BIOS settings). Usually you do this by finding the CLR_CMOS pins on the motherboard (there will be 3, and 2 will connected with a little plastic jumper). After you find it, power-off the computer, disconnect the power cord, press the "on" button (to clear any latent charge to the board), pull the plastic jumper off pins 1 and 2 and place it over pins 2 and 3. Leave it a few seconds, then replace the jumper to pins 1 and 2, connect the power cord, power-on the computer, and enter the BIOS (using the delete key, or on some boards, the F1 or F8 keys). Reset the system password, save and exit the BIOS.