Disk not formatted error on Mac can show up while you are trying to copy or move that file to that particular volume of Mac. You will also face trouble in accessing the files and opening it. The error is happening due to the corruption of the drive and to fix that it need to be formatted, so the operating system is urging you to do that. You can use the disk utility to format the drive and fix Disk not formatted error but the process will also erase all the files saved in the drive. There is no need to panic for the lost data as the time machine backup can be used which saves all the copy of the files in an external drive. However if the time machine does not work then you can use the Mac data recovery software. The software can restore the lost data easily and effectively but you have to prevent overwriting of data. So you have to perform the recovery immediately after the formatting. The software has simple interface which is easy to handle that means now you will not have any difficulty in fixing Disk not formatted error and recovering your data. So download the software now.