There are several occasions when your computer will need to be completely wiped. These include prepping a computer for a new operating system, selling it or preparing it for disposal. There are many software solutions that will format your hard drive, save over it and then format it again. This technique is by far the safest because it will make all data unrecoverable on your drive. Fortunately, if you have a Windows operating system there are several quick commands you can do to wipe your drive without purchasing additional software.
Locate the Start menu icon in the lower-left corner of your desktop. In Windows Vista, it will be the circular Microsoft icon.
Open the Start menu by left-clicking "Start" or the Windows Icon. This will open a drop-down menu with a list of all installed programs as well as a Search/Run command line.
Using the Search/Run command line, use the command CMD. This will open the DOS shell command prompt or System32 command prompt. The name varies depending on your operating system, but for all intents and purposes it is the same dialogue box.
Left-click the new dialogue box which will have a command line in the format C:\User\ComputerName.
Type in the following argument to format your primary hard drive: "format c: /q." This will initiate the quick format of your computer that will delete your file structure and data but keep Windows intact.
Insert the Windows Recovery CD into the proper drive. You will be using the Recovery CD to write over your deleted data and file structure.
Press the CTRL+ALT+DEL keys together (at the same time) twice in rapid succession. This will initiate a quick reset, bypassing the Control Panel. If the Control Panel comes up, choose "Reset Computer."
Wait for the computer to reset. You will see that the computer will load from the Recovery CD. When prompted, select the "Format FAT-32" option to write over all of your old files and restructure your hard drive.
Some restricted government software is capable of recovering data from a drive that has only been formatted and written over once. You may perform this operation several times, making your data completely unrecoverable.
Be very careful using the CMD prompt. Most commands will not require a confirmation, meaning they will take effect immediately. This could result in your incorrectly formatting a hard drive, making it inoperable.