So I have an old hard drive with windows xp and personal files on it. I want to wipe it clean and put windows 7 on it and us it as a secondary computer. What is the best way of doing this? Also I was told once something is put on a hard drive it can never be erased, is that true? If it is what would you suggest for just removing the data and restoring windows so i can have it run clean and fast as possible.