The hard drive in your PC or laptop holds all of your data and applications. It is kind of like long-term memory for a computer. Just like in the movies, even when you erase that data, remnants are left behind making it often possible to recover the data long after it has been deleted.
How is this possible? Well let me explain how Windows (and some other operating systems) store data on your hard drive. Instead of one giant container, think of your hard drive as being made up of lots of smaller containers or blocks. Each block contains fragments of a single file. As an example, let’s say there is an MS-Word document named “Tennis Schedule.docx” stored on your hard drive, and it is taking up 6 blocks. Windows also keeps an index system which tells it which blocks are being used to hold your Word document. When you delete the document “Tennis Schedule.docx”, only the entry in the index system is removed. The blocks containing the actual document data are still intact. In fact, the blocks will remain intact until Windows decides to reuse those blocks for something else.
You may ask, “why does this matter”? Well, since the file data still exists on this drive the data can often times be retrieved by using sophisticated software or hardware. This means it is possible to take a look at all that personal data on your hard drive you thought you formatted.
Don’t worry; there are some steps you can take to make sure your old data is permanently destroyed.
- Have your old hard drive commercially destroyed. There are recycling and data destruction facilities with equipment which will literally shred an old hard drive as if it were a piece of paper. With your drive in a hundred pieces it is doubtful that the most dedicated data thieves will have any success getting at your old data.
- Securely wipe your entire drive. There is software available which can replace the contents of each block with new data. By doing this, the data retrieved should be the last value stored in each block instead of your old data. Active’s Kill Disk (http://www.killdisk.com) has a free version which allows simple hard drive wiping. The paid versions allow for better protection.
- Drill holes in your hard drive. Drilling three or more holes through the hard drive’s platters (round spinning plates inside the hard drive) at different distances from the spindle (in the center of the platters) will effectively make your drive unreadable. Make sure you use a good drill bit, preferably diamond tipped.
Doing any one of these will help ensure your old data will not be recovered. Whether I’m having the hard drives commercially destroyed, or I’m drilling my own holes, I always prefer to use a secure erase software to replace the data on my drive (for at least a single pass) first.