How to Wipe Everything Off a Hard Drive Except the OSby Avery Martin
Both Windows and Mac systems provide simple methods of removing everything off the hard drive. The most efficient method to ensure that all data has been removed involves a complete reinstallation of the operating system. If you don't have the recovery disks, or can't reinstall your operating system, you can delete everything manually. Manual deletion requires the creation of a new user account and removal of all your installed applications. However, it also prevents the need to use installation media, recovery partitions or online recovery options.
Click the Start button and select "Control Panel."
Type "Recovery" in the search box and select "Recovery" from the list of results.
Click "Advanced Recovery Options" and select "Return Your Computer to Factory Condition" or "Reinstall Windows," depending on the settings configured by your computer manufacturer.
Click "Next" and follow the prompts provided by the wizard. In some cases, you may need to insert the original Windows 7 installation disk provided by the manufacturer.
Click "Restart" when prompted and wait for Windows to reboot.
Click the "Start" button. Select "All Programs | Accessories | System Tools | Disk Cleanup."
Select the "Disk Cleanup" tab and choose "Clean Up System Files."
Check the "Previous Windows Installation(s)" box and click "OK." Confirm you wish to delete the files by selecting "Delete Files."
Click the Apple menu and select "Restart." Hold down "Command-R" while your Mac restarts.
Choose a network from the "Wi-Fi" menu to connect to the Internet when the Recovery Console launches.
Select the "Disk Utility" option and click "Continue."
Click on your hard drive and select the "Erase" tab. Select "Mac OS Extended (Journaled)" from the Format pop-up menu. Type a name for your hard disk. Click "Erase." To ensure that your data can't be recovered, click the "Security Options" button and select a method of deletion. The more times you overwrite the free space, the less likely the data can be recovered. However, several rewrites may take a significant amount of time to delete an entire disk.
Select the "Disk Utility" menu and choose "Quit Disk Utility."
Click "Reinstall OS X" and follow the prompts to reinstall Mac OS X Mountain Lion.
Manual Restoration on Windows
Click "Start | Control Panel | Programs | Programs and Features." Click on each available application and click "Uninstall" to remove the program.
Click the Start button, type "MMC" into the search box and select "Microsoft Management Console" from the list of options.
Select "Local User Groups." If you don't see this option, click the "File" menu and "Add/Remove Snap In." Click "Local Users and Groups" and "Add." Click "Local Computer," "Finish" and "OK." Provide administrator credentials, if necessary.
Click the "Users" folder, "Action" and "New User."
Select the option to create an Administrator account and provide relevant user information and click "Create." Log off and then log in as the new user you just created.
Click the Start button, then "Control Panel." Click "User Accounts" twice and then select "Manage User Accounts." Provide administrator credentials, if necessary.
Click the "Users" tab under "Users For This Computer." Select each user account and click "Remove," "Yes" and "OK." If you wish, use a third-party application such as CCleaner, Eraser or FreeRaser to securely delete any data that was removed form your system.
Manual Restoration on Mac
Click "Go" from the Finder menu, then "Applications." Drag any applications without uninstallers to the Trash. Launch the uninstaller for any application that contains one and follow the prompts to remove the program.
Click "System Preferences" in the Dock. Select "Users & Groups" in the System section.
Click the "Lock" button and provide administrator credentials, if necessary. Click the "+" button and select "Administrator" in the New Account drop-down menu. Provide a full name, account name and password in the required fields and click "Create User."
Log off your current user account and log in as the new user.
Click "System Preferences," "Users & Groups" and select the "Lock" button. Provide administrator credentials, if necessary.
Select a user account and click the "-" button. Select the option to "Delete the Home Folder" and check the "Erase Home Folder Securely" to prevent data recovery. Click "Delete User." Complete this for each old account.
Click "Go," "Utilties" and "Disk Utility." Click on your hard disk from the sidebar and select "Erase Free Space..." Drag the slider between "Fastest" and "Most Secure" to set the level of deletion you want. The middle option allows a 3-pass secure erase, which is suitable for most personal users.
- On Windows machines, download a program such as CCleaner, FreeRaser or Eraser and follow the instructions to securely delete the free space on your computer. Otherwise, old files and folders may be recoverable by disk recovery utilities.
- Back up any important files by dragging them to an external hard drive before restoring your operating system. Otherwise, all of your files and data will be lost.