How to wipe a hard drive but not the operating sytem?

There are some instruction given below on how to wipe a hard drive:

• Click the "Start" button on the XP system tray, then > All Programs > Accessories > Systems Tools > System Restore. Choose this item on the list: Restore My Computer To An Earlier Time. Click "Next".
• On the dialog window, there is a calendar of the current month. Look for the highlighted days in the current month, those are days with a restoring point. Click a date, the restore points created on that day will appear on a list.
• Click the restore point on the list for that day, to which you want to return your system. Click "Next".
• A warning message will remind you to close all programs currently in use before proceeding. Click "OK" after you manually stop other programs running on your computer.
• For your confirmation, System Restore displays the time, date, and brief description of the restore point you chose for returning your system. If correct, click "Next".
  
• The restoration process will take several minutes, plus restarting Windows. You will see the System Restore reporting window, reporting the restoring status when Windows XP is running again.
• Click "OK" on the System Restore reporting window to finish task, if it says the restoration was successful. Your system is now restored to the previous point of your choice, and should be working faster.

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