Need to reformat hard drive…no OS installed

on a completely wiped hard on a completely wiped hard drive. My cd was rather scratched I do not have another xp pro I do not have another xp pro cd, but I do have a fresh windows 7 cd. How can I format the hard drive to get what is installed of xp pro off of it so that I can install windows 7? to pop the hard drive to pop the hard drive into. I need to be able to reformat from the existing computer.
Thank you
