Your question is actually quite interesting. "Erasing" is an existential quality!
When you "Delete" a file, normally it will go into your "Waste Basket" or "Recycle Bin". At this point its still there exactly as it was before. It can be instantly resusitated no matter what you do, until....
When you "Empty" your Waste Basket, the space that is taken up by that file is freed up for reuse, but it's all still there, and if you're lucky, or are just careful and quick, the right program can reconstitute it quite easily, until....
Its overwritten by something else you create. But even then, as you've heard from stories about what the FBI and NSA can do, its still really there! That "1" on the disk, really is just "55% 1 and 45% whatever it used to be" and really smart programs can resuscitate it! Now the more you overwrite it, the harder it is to resuscitate, but at some harder and harder to retrieve level, its still there, until....
You take a sledgehammer to it, or as the government does, grind it into little tiny bits. But even then, its *still there*, its just about impossible to get to!
Bottom line is that its really hard to really ERASE anything!
You could have an aeroplane flying, if you bring your blue sky back,
Buffy
