File information is maintained in a directory so your operating system can find it. All that “delete” does is erase the file’s reference information. Your OS can’t find it, but the data is still there.
PC World’s Cover Reveals the Truth (Photo credit: nep)
Sometimes simply deleting files isn’t good enough. In this how-to video segment, PC World explains a number of simple techniques for permanently and securely removing sensitive data from old drives before recycling or disposing of them.