"When you a delete a file, it isn’t really erased – it continues existing on your hard drive, even after you empty it from the Recycle Bin. This allows you (and other people) to recover files you’ve deleted.
If you’re not careful, this will also allow other people to recover your confidential files, even if you think you’ve deleted them. This is a particularly important concern when you’re disposing of a computer or hard drive..."
What happens when you delete a file