The term "delete" should be replaced with "archived" or "hidden" on computers so users are no longer fooled into thinking that once you "delete," the file is gone forever.
Even when you delete something in the recycle bin, it's not gone; just hidden from view. You maybe can't retrieve it, but someone else can.
Invisible files or data are called latent. Deleted files are latent. How is this, then, if deleting something in the recycle bin makes it vanish and you can't get it back?
Well, let's suppose you want to create a file and put it on your desktop. It's in active status. You save it, triggering its entry into your computer's table of contents. This master table of contents allows you to access your active file.
Now you delete it, then again from the recycle bin. This takes it off that table of contents. That's all. It's removed from this master list. But in many cases the file still exists. The empty space in the table of contents can take a new file.
Now if you create new data, say, a recipe in Word, then save it and call it "YummyVeggie," you have a new file. If you put it in the recycle bin and then delete it from there, the recipe is still on your hard drive.
However, what if you had deleted the recipe within the Word document and instead put in a different recipe then saved that document under the same name "YummyVeggie," You just overwrote the old recipe; its data no longer exists because the new data is taking up the same space in the table of contents.
To prevent a hacker from obtaining the latent data, you should encrypt the hard drive. This will scramble the data, making it useless.
Should you want to sell or get rid of the computer, first truly delete its data. This is done best by physically destroying the hard drive, or by de-magnetization of the hard drive.
You can also overwrite the hard drive's data with a special program, but this will take time, and it may not be 100 percent complete; a computer forensics specialist may still be able to retrieve some data. Though this scenario is minimally likely for the average user who chucks a computer in the trash bin, it yields greater peace of mind if you use one of the first two methods, with physical destruction (burning, sledge-hammering or using a metal shredder) being the more effective.