It depends on your situation. If you delete your files mistakenly, you can check if they are still in the Recycle Bin and put them back. Besides, if your data is lost due to Recycle Bin emptying, hard drive corruption, inaccessibility, or so, you can check if you've backed up the data at another destination. Then, restore the lost files from the backup. Or else, you need to use the hard drive recovery software.