First, back up your saved files ! Remove any cards you will no longer need - sound, network, etc that may be built into the MoBo that you may want to use. Then you can change your MoBo and CPU and hope that XP just installs all the new hardware. IF it works and XP installs all it needs, probably with several reboots, then install all the new MoBo drivers (4in1 stuff).
It may work but don't be surprized if you need to wipe the drive and re-install everything. Don't forget to BACK UP your stuff before you try this.
For it is not what is seen, but what is not seen. 😱