OS X Mountain Lion: If you’re asked for an administrator name and password
To complete certain tasks, you must enter the name and password of an administrator to verify, or “authenticate,” that you are a user with administrator privileges. If you’re in a secure environment where smart cards are required, you must insert your card and enter a personal identification number (PIN) instead of a password. You should always be sure you know which app is requesting this information.
If you don’t know an administrator name and password, ask the person who administers your computer for help.
The user you create when you set up OS X is an administrator. You can also add additional administrators on the computer. If you set up the original user but don’t remember the password, see this help topic: