If you think when you empty files from your Windows recycle bin or directly delete files from USB flash drives and other digital media connected to your computer that those files are removed permanently from your computer you are completely mistaken. When you delete a file by either of those two means, all that happens is the file name is removed from the area allocated to that file and replaced with notations that the space is available for new data.
Until those sectors of your computer’s internal hard drive or other digital media connected to your computer are overwritten several times with new data, anyone with a reasonably powerful data recovery tool can search through all of your information still available on your computer’s hard drive and copy that information. Obviously the entire point of deleting a file is to remove that information from public view. For this reason there are available quality programs to delete files forever. Generally referred to as a file shredder, this software will purposely overwrite deleted file sectors many times over with random information. This effectively erases the files in such a way as they can never be reconstructed.