hello - My nephew recently purchsed an old iMac (tear drop shaped) from his high school. Since it was in a school setting the control panel is locked -- We are guessing to keep students from making any changes. However, since it is now for private use how do you gain access to the control panel? this is running 9.2 or 9.4 OS --- not sure off hand but appreciate any info on getting into the locked control panel. thanks !