If you empty the Trash the files are gone. If a program does an immediate deletion rather than moving files to the Trash, then the files are gone. Data recovery is possible but you cannot process any additional writing operation to the hard drive but just shut your computer down. Actually when we delete files, the files themselves are not really erased-only the directory entries are deleted. The space which was occupied by the “deleted files” has been returned to the system as available for storage, but in fact that the “deleted files” are still on the drive. But if you write any data into the drive will overwrite the space of the "deleted files" and these files will be lost permanently. Also if you save a file into the hard drive with the same name of one file which has already put into the drive, the old one will be overwritten by the new one and cannot be recovered.