why do you want xp you could save some headache and use a virtual box but if you are set on xp and this is a newer pc you will have to slipstream all the drivers you need and service pack 3 for it to work there are some you tube videos on this if it was me i would buy a 30 gig harddrive to install it on because you may have some problems if you are new to this .
i would unhook my hdd i have seven on and hook up a 30 or 60 gig hdd and use that .
you will also need the sata drivers for this to work the easier method of having xp is a vm and a cracked xp iso
you will need to find xp drivers for all you components odd card reader sata drivers "every driver" and xp pro service pack 3 and your good to go
i know it may sound hard but youtube has videos on this search for CareyHolzman How to Build a Gaming PC 2012 - Part 3b great tut on this subject this will show you exactly what needs to be done !!! your motherboard has to be xp compatible and you will need this drivers check that video