Anytime a file is deleted from a hard drive, it is not erased. Even though you have emptied your Recycle Bin or the Trash Can, the files are still located in the hard drive and can be retrieved. The only thing you have deleted is the bit of information that points to the location of the file on the hard drive. The file becomes invisible to your system so it does not know where to find the “deleted” files.
The good news is, if you have accidently deleted some important files you can have a technician retrieve them for you, or there is software available if you want to do it yourself.
The bad news is, if you think you have deleted all your important data before you gave away or threw out your computer, remember, it is easy to retrieve your deleted files. This is also the case for any electronic devises with built-in memory, such as smart phones, iPods, digital cameras etc.
The safest way to erase all your data is to reformat the hard drive. There is also file erasing software available that will get your job done clean.