How to Wipe hard drive on my Windows 7 computer?

On Windows 7, the most common and reliable built-in method is to use the "Clean all" command in Diskpart. This completely overwrites the drive and makes data recovery practically impossible.

Here’s how:

1. Boot your PC with a Windows 7 installation DVD or recovery USB.
2. When the setup screen appears, press Shift + F10 to open Command Prompt.
3. Type the following commands step by step:

• diskpart

• list disk (note your hard drive number)

• select disk X (replace X with the number of your drive)

• clean all

This will overwrite every sector with zeros and securely wipe the drive. After it’s done, you can exit and reinstall Windows (or leave it blank for the buyer).