Swapping hardware is a sinch usually. What you do is before you switch the mb, immedately boot into safemode. Now all you want to do in here is uninstall all hardware via the device manager. And I mean EVERYTHING. Anything it'll let you remove, do so. This includes chipset drivers, busses bridges, processor drivers anything.
Now power down and install your hardware.
Now boot into regular windows and xp will automatically detect all of your hardware as if it was installed the first time. You may run into glitches during the install process, but once xp becomes bootable again you can sort out minor annoyances.
Here's the catch...... this will probably be the last time you can do this type of upgrade. Xp can only do full hardware changes (motherboard) a few times.