Deleting a file from Windows does not destroy data beyond recovery. When you "delete" a file, the area used to store the information from the file is only marked as being available for other files, but the file content remains on the free space of your hard drive. Windows employs a user-independent pattern to overwrite deleted files so it may take weeks, or months, before a file gets fully overwritten.
This poses a serious privacy issue, because your deleted files can be recovered in the meantime. Hackers, co-workers, family members, laptop thieves, service provider employees, people who find you lost laptop, etc, can all have access to your deleted confidential data. Let's have a look at some scenarios when this issue can compromise your privacy.
Sensitive files
Need to make sure that some highly sensitive files, such as, passwords, banking details, medical records, business plans, trade secrets, etc, are gone forever from your PC? If you rely on the usual Windows deletion that basically means you only move your confidential files from one location to another on your hard drive!
Compromising browsing history, cookies, cache, etc
One of the easiest way to leave compromising and revealing traces behind is by surfing the web. Your browser logs every single thing you do on the Internet: the sites you visit, images you view, videos you watch, files you download, search queries you enter, passwords you handle, forms you fill out, credit cards you use and so on. So, when it comes to permanently deleting your history, don't leave it to Windows!
Emails
There are business, or private emails you want to make disappear from your inbox, sentbox, and trash for good? Neither web-based, nor PC-based email readers can guarantee that, even after "deleting" those mails. All that happens is that your deleted emails end up on the free space of your hard drive from where they can easily be recovered.
Skype, Google Talk, Windows Live Messenger, Yahoo Messenger, etc.
Did you exchange confidential information in a chat conversation and want to make all of its traces disappear? The above mentioned services keeps copies of your conversations on your hard drive and once again, simple Windows deletion won't remove them securely.
Social networking
Just sent someone a compromising image in a Facebook message? By deleting the message you want to make sure that your actions can't be tracked? The bad news is not only that there still will be a cached copy of your deleted message on the Facebook server for a while, but also that your history will have logs of you sending that message from Facebook with the exact date and time of sending and the browser used. Simple Windows deletion won't rid you from those traces for good!
Browser sync
Feeling relieved having deleted your compromising browsing history from your primary PC? Not so fast. If you enjoy the convenience browser sync offers you, be aware that your history got copied to all the devices you keep yourself signed into, so you need to fight for your privacy on multiple fronts!
Laptop theft or loss
Just got your laptop stolen, or lost, but at least your sensitive business files were deleted last week? The bad news is that it's very likely those deleted files are still on the free space of your hard drive so thieves, or people who found your laptop can recover them from its hard drive.
What's the definite solution to tackle that issue?
To securely erase files, you need a tool like east-tec Eraser, that overwrites the data from the file with specific patterns defined by well known governmental and industrial standard for the secure deletion of sensitive information, such as US Department of Defense DOD 5220.22-M standard, Peter Gutmann, Russian GOST P50739-95, German VSITR, etc.