Alternatively, boot from the ultimate boot CD, free ISO file download at
http://ubcd.sourceforge.net/. Convert ot physical CD via a program that supports burn-from-image, such as Nero or Easy CD Creator. It has several disk erasing/preparation tools, which can delete paritions, make new ones, reformat, etc. For use with XP by itslef, you probably want to erase everything on the hard drive, including paritions tables, boot record, etc. Then re-write as if this was a fresh (blank) hard drive from the manufacturer.