Have you noticed error code 120 when dealing with locked files? Do you want to know that why does it happen and how to solve this problem in a convenient way. If yes then i must tell you that this post where you reached is the right place, as here you will get all help which you requires. Let me tell you that the coming of error messages is not a big issue in Mac computer. When nay user is trying to transfer any from one volume to another volume and during this process if any interruption occurs then this may effect the files. All the important files will became locked and the user will get error code 120 when dealing with locked files. The reason behind this is abruptly system shut down at the time of file transferring. This could be due to presence of malware in the computer. The user who got error code 120 when dealing with locked files are really worrying about how to unlock the locked files. You will be happy to know that a third party tool which is known as Mac data recovery software can help you in this situation. It will make the locked file unlock in an easy way.