Kirk from Utah writes:
When you delete something, where does it go? How do you delete something completely off your computer?
Great question, Kirk. In fact, a lot of users are really paranoid about whether sensitive data can be recovered from their system’s hard drive, even if you have deleted it months ago.
By default, Windows keeps all your deleted files and folders in “Recycle Bin” – a special system folder which is basically acts as a trash bin for your system. The Recycle Bin acts as a storehouse for files and folders which you have marked as “unnecessary” or “useless”. However, please note that deleting a file or folder does not necessarily delete it permanently from your computer’s hard drive. The specific file or folder in question goes to the “Recycle Bin” folder and it can be restored, as shown in the following example:
To permanently delete a file from your computer’s hard drive, you must open the Recycle Bin folder, select the file in question and do a force delete. There is no easy undo after this, so you should double check before proceeding.
So here’s an easy trick. When you want to “permanently” delete something from your computer’s hard drive, hold the “Shift” key on your keyboard and hit the “Delete button”. The selected file or folder will be deleted permanently as Windows will not put it in the “Recycle Bin” folder, like it does for other files when you hit only “Delete”.
However, depending upon the state of the operating system, there can be situations when it becomes very much possible to recover a file or folder – even if you have permanently deleted it from the Windows “Recycle Bin”. For example, if the system you’re using has a file recovery application installed, there is a high chance that the application might bring back a deleted file or folder… even after weeks.
See, when you delete a file or folder from Windows, only the link to the data is destroyed. There is still a chance that the actual data is lying somewhere on the disk, completely inaccessible to you. This is when file recovery programs, such as Recuva come into the scene. These file recovery programs can sometimes restore the old links, which might bring back an old file or folder that was deleted months ago.
Hence, for a completely secure deletion, you have to ensure that both the data and the links to the data is destroyed and overwritten. A simple way to do this is to install Eraser  on your system.
Eraser is one of the best known data removal tool for Windows. It securely deletes every trace of information about a given file or folder, and completely removes sensitive data from your hard drive by overwriting it several times with carefully selected patterns. Once you have deleted a file or folder using Eraser, no file recovery program can restore it.
Once you have installed Eraser, right click a file or folder and choose “Eraser > Erase”
A full format of the system also deletes all files and folders and recreates the file system from scratch. However, a full format is a really long route, and makes sense only when you are rejecting or selling an external hard drive and want to ensure every piece of data is killed.
We hope this helps,