Undelete overwritten files requires that the original content still exists on the disk. Once a file is deleted, the space allocated to it can be used for storing other information. If the disk space allocated to the deleted file is not occupied by any other information, recovery software will help to get back the file. However, if new data overwrites the original data of the file, it will be extremely hard to retrieve it. Stop using the affected disk and check for backups or previous versions of the file.
