Please read the FAQ post entitled "Getting to know Eraser 6". I am somewhat surprised that you can't find it. There should be an Eraser icon on your desktop, and another, smaller, one in your system tray.
Thanks for your help.
I went into the operating system (XP) and updated it. Then I downloaded Eraser again. This time the install went through.
I am now happily erasing my old computer so that I can dispose of it safely! Thanks! Thanks! Thanks!