I would like to remove and change vista os to windows xp os for my compaq laptop.?

i format the hardisk and during the installation of windows xp os, the pc tells me there is no available hardisk.please help me what should i do?I would like to remove and change vista os to windows xp os for my compaq laptop.?Run Fdisk firstI would like to remove and change vista os to windows xp os for my compaq laptop.?Format your drive before installing XP