do u want to backup some of ur files like music, pictures etc? if no, do this, if yes, burn it on a CD/DVD
ok, first u gotta have a copy of Windows XP of course, then u insert the CD in your CD/DVD ROM, go to BIOS and set to "boot from CD/DVD drive", save the settings and exit BIOS, when it boots from a CD there will be instructions what do u want to do, like, "Install a new fresh copy of Windows XP", "Repair Windows XP" and stuff like that, then when u come to part when u have to format the HDD, select "format to NTFS system file", rest of the stuff it like just waiting and clicking the "Next" button, questions?