Before selling or disposing of your computer - whether it is working or damaged - you should delete sensitive documents and data. For absolute safety, you should do this even if you just leave them somewhere around your home, such as a garage or a storage room. One thing you will never know is who will get their hands on their old computers.
If you think you just need to delete sensitive documents and consider it safe to dispose of your system, this is not entirely true. The remaining marks on your hard drive may exist beyond what you envisioned. The truth is emptying the Recycle Bin or even reformatting a hard drive is not secure enough.
You can still save email messages on your computer, including important logins and sensitive content, website passwords that are remembered in web browsers as well as passwords stored for services and other applications. All of that can be restored even though Windows cannot boot. It is possible for other users to use a live CD to restore or bring the hard drive in your computer to another computer.
All problems belong to the hard drive
Remember that the one used to store all your data, files and other data is a hard drive. Basically you can remove the hard drive, the system dump is in effect and now your task is to protect the hard drive. However, you still need to delete these hard drives before removing and hiding them somewhere.
Why is deleting and formatting not the same as "wipe" the hard drive?
Hard drives are a type of device used to store digital data. Files are stored on magnetic hard disk surface and rotate magnetic disks in hard drive box. Hard drives change the magnetic properties of the disk surface to 1 or 0 when reading or writing data. Therefore, all data on the hard drive will be saved as basic binary data. For example, when the system stores data such as photos, music, etc. on the hard drive, rows 0 and 1 are recorded on the magnetic disk.
When deleting a file, the numbers 0 and 1 will not be affected, only the cursor indicates the file is deleted. Therefore, you can still recover deleted files before file data is overwritten or corrupted. What about the disk format? Disk format works the same way, it doesn't really "wipe" data. You can use recovery software to recover lost files on formatted drives.
How does "Wipe" hard drive work?
To completely erase the hard drive, you should delete the binary data, which means overwriting the numbers 0 and 1 with new data. When replacing the binary data of a file and overwriting it with new data, it cannot be restored. Some specialized hard drive eraser software can fill the hard drive with a zero or random sector information, making sure that it is impossible to recover data from a "wiped" hard drive.
What to do before deleting a hard drive?
You need to do some work before erasing your computer hard drive to make sure it is completely erased without causing a problem.
- Download and install hard drive erasing software. If you are going to delete your hard drive yourself, you need an efficient and easy-to-use erasing tool. If you want to delete the entire computer, you need to make sure the software that works on the hard drive is bootable.
- Make sure your computer's battery is full. If you want to delete computer data, you should make sure the battery is full or connected to a power outlet. If there is a power failure while erasing the hard drive, this may damage the hard drive.
- Back up data to another hard drive. When you wipe your computer, all data will be lost, so you need to backup the file you want to keep on another hard drive.
Read more: Transfer data between computers
- Remember to save the software key number. The software you buy will be lost after wiping your computer data, you need to reinstall them on the new hard drive. Therefore, write down the keys of these programs so you can activate them after reinstalling.
- Download the driver. If you plan to reinstall the operating system after wiping the hard drive you need to download the drivers needed for the new system. You can go to the device's official website and download the latest driver version.
- Prepare a boot disk. If you delete your computer's main hard drive, you must perform the task without booting up the system. In this case you need a USB drive or bootable CD.
Clear data completely on Windows computer
1. Delete each data on Windows computer
There are basically two methods of deleting data: the method of selecting files to erase (cleaning) and the method of cleaning (wiping) the entire hard drive.
If selling or disposing of your computer and the data security issue is not very important to you, then you may want to consider manual deletion. Just leave Windows alone and delete all sensitive files and passwords yourself with the Shift + Delete keys. However, this method is not really safe because it may omit data to be deleted.
If you don't want to risk your data and privacy, or you don't want to do it manually, you can "wipe" your hard drive. This means that you will delete all data, including Windows, applications, documents, passwords, ... everything. This action not only deletes the data but it also makes it impossible to recover data by replacing all the old data with blank data. This method is acceptable for use by government organizations.
However, if you "wipe" the entire hard drive you can still reinstall Windows later if you have the installation disc and the product key. (Sometimes a product key is on a sticker on your computer).
We will discuss both methods. First we should review what we need to find and delete manually. Then we will look at how to "wipe" the hard drive completely.
When you press the Delete key, Windows moves the files to the Recycle Bin. Even after you Empty the Recycle Bin, they are still recoverable. This is only useful when you accidentally delete a file, and the bad case is to try to protect your data to avoid snooping or sniffing the failure completely. Free utilities like Restoration and NTFS Undelete, can make it easy for someone to recover your files.
To ensure that deleted files cannot be recovered again, you must use a file cutter (like a paper cutter in security rooms, before being discarded, it needs to be shredded). It is similar to the technique of "wipe" the hard drive. The files you take to the cutter will be completely destroyed forever.
Here are some places you can start your cleaning:
- Personal files and documents: Start with personal folders, these are folders created by Windows, such as Documents, Pictures, Music, and Videos. Then you need to clean the hard drive for any personal documents or files. Open Computer and click on the drives to directly access specific folders. You can skip the Program Files and Windows folders as these won't contain personal files.
When you find the folders or files you want to destroy, select them, right-click, and delete with the file cutter you downloaded. Do not click Delete; There will be a new section for the file cutter on your right-click menu.
- Files and browser settings: You definitely want to delete history, favorites, remembered passwords and other temporary files. In Internet Explorer 8, click Safety> Delete - Browsing History. In Internet Explorer 7, click Tools> Delete Browsing History. In another version, navigate to the favorites menu and then delete them.
- Server and email settings: If you use an email client, like Microsoft Outlook, you should delete your email and connection settings with your email server or service. With Outlook, you can delete PST files. In Windows XP these files are usually located at C: Documents and Settings \ UsernameLocal Settings \ Application Data \ MicrosoftOutlook. In Windows Vista and Windows 7, check out C: UsersusernameAppDataLocalMicrosoftOutlook.
Windows files to be deleted
- Wireless network keys and passwords: When connecting to an encrypted wireless network, you must enter the network key or password. This password will then be saved because you will not need to enter it again the next time you connect. To delete these passwords, simply delete the wireless network profile set up with Windows. Navigate to the wireless settings via the network icon in the system tray or through the Control Panel.
- Network sharing passwords: With these passwords, you can use the Network Password Recovery utility of NirSoft. This utility can scan and display all saved network passwords, from which you can select and delete them.
- Password for VPN and dial-up connections: Start by invoking the Network Connections window, possibly via the network icon in the system tray or Control Panel. Then open dial-up and VPN connections to make sure passwords aren't saved. If they are already selected, deselect the Save Password option or clear the connection with it.
- Restore points: You just need to disable the System Restore feature of Windows. Open Control Panel, find System Tools, and open System Restore settings.
- Remote Desktop: If you have used the Windows Remote Desktop feature to control a remote computer, you need to make sure it does not have a password saved. Click Start> All Programs> Accessories> Remote Desktop Connection.
- Temporary files: You can use the Disk Cleanup utility found in Windows: click Start> All Programs> Accessories> System Tools> Disk Cleanup. Surely you should do this last as it will take good care of the Recycle Bin.
There may be many other programs or software that may save passwords or sensitive information. Therefore, you need to delete sensitive information or remove the program. Here are some other applications you may have installed and need to check:
- Financial and accounting software
- FTP or SSH client programs
- Instant Messengers (such as MSN, Windows Live, Yahoo Messenger, ICQ, and AOL)
Last but not least, you should remove the password to protect your Windows account. Open the User Account setting through the Control Panel. You can also delete other Windows accounts too.
2. Erase data completely on Windows hard drive
Delete data completely on hard drive using command
If you are afraid of installing additional software on your computer, you can use the tools available in Windows. To completely delete the data on the computer, do the following:
- Go to the command prompt window by pressing Start> Run> cmd or Windows + R> cmd
- Enter the command: Cipher / w: C
- / w: Delete any data
- C: Drive needs to erase data, you can change to other drives like D, E to erase all data on the computer
Erase data on the hard drive completely by resetting the PC
This method uses the reset feature in Windows 8.1 or Windows 10 during the reinstallation of the operating system. It has an option to delete everything on the hard drive. The steps below are done on Windows 10, if you use older versions of Windows, you can try other methods.
Step 1. Click on the Start menu and select Settings. On the Windows settings window, click on Updates & Security.
Step 2. Click on Recovery on the left navigation option and then click on the Get Started button in the Reset this PC section.
Step 3. Select the Remove everything option to remove all personal files, applications, and settings.
Step 4. Select Remove files and clean the drive when asked if you want to clean the hard drive. This process can be a bit time consuming, but make sure no one is able to recover these deleted files.
Step 5. Click Next> Reset in the next step to complete the process.
Erase data on the hard drive completely by software
If you remove the hard drive from a computer and plug it into another computer, you can use a tool like Disk Wipe in Windows. This is a tool that can erase hard drive partitions, but does not delete the partition that is installed and running Windows.
To erase the drive with the operating system installed on your computer, you must create a bootable disk or bootable USB and boot using that utility. This may allow you to work even if Windows cannot be started. Active @ Kill Disk is an example of this type of tool. Or you can use DBAN also completely free. The illustration below will use Active Kill Disk to do this.
After installing Active Kill Disk, go to Start> All Programs> Active KillDisk> KillDisk for Windows. A compact and very simple interface displays, and you only need to select the hard drive (internal or external) that you want to delete located on the left side of the screen.
When a drive is selected, the Kill button above will work. Click the Kill button. Now the Kill form appears, allowing you to choose options for erasing the drive, then clicking the Start button. Note that you can also choose a pass method in the form of a pass.
Now, all you have to do is wait for the disk to format. After success, the drive is now completely clean like a new hard drive and there is no data when using programs to try to recover data.
3. Clear data completely on macOS
OS X has a built-in Disk Utility utility that safely erases hard drives. However, the process varies, depending on whether you are erasing an internal or external hard drive.
For internal hard drives
To get started, insert the first installation disc that came with your Mac when you purchased it. May be labeled the MacBook Install Disc.
Restart the Apple Logo computer> Restart. Immediately after the reboot, when you hear the boot sound chime and see the Apple Logo, hold down the C key. Continue holding the key down until you see the spinning wheel below the Apple logo.
By holding down the C key, we will boot from the installation disc, rather than the hard drive. Once the OS X installation screen appears, click Continue to the next screen. Move the mouse to the top of the screen. This will activate Mac OS X, a navigation bar appears on the screen. Select Utilities> Disk Utility. After Disk Utility opens, select your Mac's internal hard drive from the list of devices, located along the left side of the Disk Utility window. Click the Erase tab.
Set Format to Mac OS Extended Journaled and enter a name for the hard drive. Next, click on the Security Options option ... From here, you can choose a level of deletion. 35-passes take a long time, but it is the safest, as it overwrites on the hard drive 35 times. For a quick erase (less secure than a 35-pass, of course), choose 0-pass or 7-pass. Finally, click the Erase button ... to delete the data on the drive.
4. For external hard drives
The process of wiping an external hard drive is the same as above. However, it can be done directly in OS X so you don't have to reboot and boot from an installation disc. Simply navigate to Finder> Applications> Utilities> Disk Utility to access Disk Utility.
I wish you successful implementation!