There may be many reasons that computer owners may wish to clean up the contents on their computers or delete data which could include any or all of the following:-

  1. Data may be confidential;
  2. Computer drives may have been compromised;
  3. Computer may be being upgraded and previous computer being sold; and,
  4. Computer may include pirated software or files and owner wishes to become fully compliant

1. Cleaning up a computer’s hard ware permanently 

Computer Delete Function

Contrary to popular belief, there is no such thing as a categoric and final delete function on a computer. Files may, of course, be dragged to a recycle bin and be emptied in that bin. However, all this does is clear the icon and remove the file's name from a hidden index of everything on a computer, and informs Windows that the space can be utilized for another purpose. Until that space containing the deleted file or item is actually utilized for something else, the space will continue to contain the contents of the supposedly deleted information, similar to a filing cabinet that has had all of its labels removed but still contains the original files. And this of course is why, if you have the correct software and act speedily, it is still possible to restore information that has been deleted by accident.

Deletion tools enabling total cleaning of information and data

Secure deletion tools usually replace or overwrite data as opposed to deleting it. Taking the documents stored in the above mentioned hypothetical filing cabinet assumes that they are written in pencil, and consequently the secure deletion software can be used to both erase the actual content and overwrite every word. However, pencil lead can still be read albeit poorly as can digital information, even after erasure and being overwritten over. Accordingly, deletion tools recommended overwrite files with random data several times. This process is called wiping, and the more times the actual data is overwritten, the more difficult it becomes for recovery of the original content. Experts consider that three or more overwriting phases should be made; and some would go as far as to recommend seven or more.

Cleaning and Deletion of Files

The two most common ways of deleting sensitive data from a computer’s hard drive or storage device can be summarized as the deletion or wiping of a single file or alternatively the deletion or wiping all of the 'unallocated' space on a drive. When considering the hypothetical example mentioned earlier-the long report that may have left incomplete copies scattered throughout a hard drive, even though only one file is visible. Wiping or deleting one file itself may guarantee that the current version is completely removed but does not mean that other copies still remain somewhere on the drive. In fact, there is no way to target those additional copies directly, because they are often not visible without special software. By wiping or deleting all of the blank space on a storage device, however, it is possible to ensure that all previously-deleted information is destroyed.

Eraser is a free and open-source secure deletion tool that is extremely easy to use. Files can be wiped with Eraser in three different ways: by selecting a single file, by selecting the contents of the Recycle Bin, or by wiping all unallocated space on a computer drive. Eraser can also wipe the contents of the Windows swap file. (space on a hard disk used as the virtual memory extension of a computer’s real memory.

2. How to clean up software and files on a computer permanently?

Wiping the entire contents of a storage device

What if you need or wish to wipe a storage device completely?  When you dispose of or sell an old computer, it is advisable to remove its hard drive forcing the computer's new owner to purchase a new one. Alternatively, prior to sale or disposal, the drive should be wiped with Eraser before handing it over. If the old drive is to be thrown away or recycled it is advisable to destroy it physically.

The simplest and most efficient way to completely clean an entire drive is to remove the drive and put it into an external USB 'drive enclosure,' which can then be plugged into any computer with Eraser installed on it. At that point, delete the full contents of the external drive and then use Eraser to wipe all of its unallocated space. Unfortunately, this is a time consuming exercise.

Sometimes the best means of wiping data on a rewritable CD or DVD or even a non-rewritable disc is to destroy the disc itself. It is very difficult to destroy the contents of a CD or DVD completely but a strong pair of scissors or a paper shredder should do the job nicely. This is not totally fool proof, but it does go along way to achieving the necessary result.

3. How to destroy a hard drive?

Contrary to other views, the destruction of a hard drive physically is probably the best and safest way of ensuring that the data held on it is not accessed and re-used again.

Necessary Steps

Step 1:  Wipe the hard drive using a utility tool which can be downloaded free from the internet.

Step 2: Physically remove the hard drive from the computer.

Step 3:  A relatively fool proof way to destroy a hard drive is to drill through the drive completely from one side to the other, and you’ll want to do this multiple times and ensuring that this is done through the platters and the controller board.

Source: This article has been researched and written by Khun Tawee Ratanabunsin, Senior IT System Administrator to RSM Thailand.

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