Your computer has been protected by a Power On password.
If you didn't set this password then ask the person who set the password on the computer.
This password is near impossible to crack, try various names, pets, kid's names, family names/places, street names etc. There are no back door passwords and the password is not stored in the BIOS and removing the BIOS battery won't erase the password.
The password is stored on an EEPROM chip and you need electronic knowledge to build an EEPROM reader, then pull your laptop apart, solder the reader to your laptop, connect the reader's connector to a working computer, and run a program to read the contents of the EEPROM, identify the password from the downloaded data, unsolder the reader, put the laptop back together, boot up and insert the password. You can now enter the BIOS and change the password or remove it.
For further info goto http://sodoityourself.com
The Power On password and the Hard drive password are designed to prevent unauthorized access to the laptop and the data that is stored on its hard drive.
Removing the hard drive from the protected laptop and inserting it into another laptop will not work, you still cannot access the data on the hard drive without the correct password.