How to unlock a photo in camara
The protect function allows a user to protect a picture from accidental deletion. To unprotect a picture on your camera, scroll to the protected picture that you want to delete, then press the Menu button (the button to the right of the Play button.) Scroll down the menu and you should come to an option that allows you to Protect/Unprotect the picture. Since your picture is currently protected, deselect that option. You should then be able to delete the picture normally.
Alternatively, you could also format the memory card, however this deletes ALL photos and data you have on the memory card. If you are trying to completely clear the memory, this is the best way. After turning on your camera, simply press the Menu button, scroll to Setup, then scroll down to Format. Select Format, it will ask you if you want to format the memory card, or the camera's built-in memory. Format whichever one you want to clear, if you are using a memory card then your pictures are stored on the memory card. It will take a few seconds to format.
Hope this helps.