http://y7yea4pmqqtznb33qiugvysyn2bob5v62e4pvoadoibrwkq3tsddjeyd.onion/zh-hans/module/how-delete-your-data-securely-windows
Your operating system probably already has software that can do this for you—software that can overwrite all the “empty” space on your disk with gibberish and thereby protect the confidentiality of deleted data. Unfortunately, due to the way SSDs, USB flash drives, and SD cards work, it is difficult, if not impossible, to securely delete both individual files and free space where some operating systems may leave parts of files.