Hello, I bought used Laptop computer a while ago and when I used it the computer had multiple errors so I decided to wipe it clean and install Windows XP. Now on startup it shows 2 windows operating systems and always asks which one I want to use. Lately after multiple viruses and my wife using it the computer is running bad and I want to wipe it again and reinstall XP but this time I want to make sure that the Harddrive is completely clean first. What can I do to make sure there is nothing on the harddrive before I install XP again? After the last XP install my 20gb harddrive only had 9 gb left so there must be alot of info somewhere.