When you delete a file, format your hard drive or erase any data on any type of media in the traditional manner, you might be surprised to know that the file still exists. In this way, you can think of files on a hard drive as a phone book. You can see the files in a listing (such as what is shown in My Computer or Windows Explorer). Each listing in a phone book lists the address and phone number for that person so that you can reach them, and by removing the listing from the phone book, it doesn’t mean that your friend doesn’t live there anymore.

Deletion basically removes the “directory listing” for that file, but the file still exists. So, now it’s difficult to “get in touch with”, because the listing is not there and you can’t get access to it anymore without recovering it. The file still physically exists and will until other data is written where the original file resided.

It is possible for the file or parts of the file to be recovered even after new data is written onto the same area of the hard drive where the original data resided. Though the process at this point is so difficult you have to pay for data recovery. The service is very expensive, because it requires specialized equipment and software. Only experts may be able to recover data at this point.

Each time new data is written where the original was stored, it becomes more difficult. If you delete an important file that you need to recover, try not to install any software or save any files at this point. You don’t want anything writing to areas of the hard drive where that file is still intact at. You could download free software or buy software to recover the file and the odds are that you will be able to recover the file at this point. Though just by installing the software you run the risk of writing to areas of the hard drive where your file is located and losing it. So another option may be to install the software on another computer with a different hard drive, connect your hard drive to the other computer and run the software on it to locate the file.

The simplest method we have of getting rid of files is to format the hard drive or delete the files. This does not actually remove the data. It does make it unavailable to you without recovering the file. Files that are deleted are somewhat easily recoverable in a lot of cases. You can go as far as to delete a partition and recover the entire partition. In the past I’ve been able to fully recover entire partitions and this took just several minutes.

There are methods of securely deleting data from a hard drive. Usually the only reason you would want to use these methods available, such as the Department of Defense’s 5220-22.M seven pass wipe is to help ensure that company secrets, government top secret information, financial records or possibly even incriminating evidence will be removed. Even these high security methods are not one hundred percent sure, but even after one pass there isn’t much hope for recovering the file unless you are a suspected terrorist or pedophile, because someone may want that evidence badly enough to pay for its expensive retrieval.

For most people that want their personal financial information securely removed, formatting is enough to prevent 99.9% of the population from ever seeing it again. That’s because odds are no one is out to get you. There are millions of people in the world that would absolutely love your financial information though. You could make the data unrecoverable by using a simple one pass wipe with software such as Darik’s Boot and Nuke.

Remember that anyone with intermediate knowledge of computers could easily recover files that have been deleted as long as the file is still intact where it resides on the hard drive. You could purchase software or download free software that will do it for you. So are you satisfied with just deleting the file? In most cases you probably can be, but it’s up to you to determine the risk and chance that the file can be recovered by anyone.

Below is a list of free software available online.

Software:
Darik’s Boot and Nuke - self-contained boot floppy/CD that securely wipes the hard disks of most computers. DBAN will automatically and completely delete the contents of any hard disk that it can detect, which makes it an appropriate utility for bulk or emergency data destruction.
TestDisk - Warning: Not user friendly. Powerful free data recovery software! It was primarily designed to help recover lost partitions and/or make non-booting disks bootable again when these symptoms are caused by faulty software, certain types of viruses or human error (such as accidentally deleting a Partition Table). Partition table recovery using TestDisk is really easy.