Post originale di: mayer ,
You have locked the firmware (Master) Password. This can be turned off in System preferences but you will need to remember the password. You may also have activated it by turning on File Vault. Use your original system installation disk and start up holding the "C" key down. If this fails, start it up in Target mode via firewire cable with another Mac and use Disk Utility and wipe the hard drive. Then start over with the system disk and install a new system. Please stay away from the master password.