Hello, in case I return the old rMBP 15" 2012 to my work place, what is the best way to erase all the data in that computer? It has a SSD drive. Should I zero-in several times? Can IT still retrieve the data after me doing that? I don't recall there is a system disk which came with the computer. I think I heard that the system installation program is in some kind of secret partition. If I zero in the drive, will that partition be erased?