ahhhh fdisk... now that is old school

they still running windows 98?

anyway you could use fdisk but... you should be able to do it from the XP install menu (either a quick format, or full format - go full)
edict:
ectualy no - your friend tricked me into making the commom mistake he/she does.
fdisk will only remove/add partition pointers to the drive - it will not do a full format (if i remember correctly

)