Error 12700 appeared when you have configure "Share Image instead of Copying it" ( http://www.ms4u.info/2009/10/share-image-file-instead-of-copying-it.html. ) .
Full description of error as listed below snapshot:-
Resolution:-
a) On the share folder of the library shares which contained the ISO image, add "Authenticated Users" with the Read permission on NTFS and share folder.