Here is info from one site
Solution 5; Microsoft SYSPREP:
I have swapped motherboards several times. The key is preparation of the old system before taking out the old motherboard.
There is a SYSPREP tool on the XP CD.
You may need to extract files from the Windows XP CD, files are located at CD:\SUPPORT\TOOLS\ in a cab file called DEPLOY.CAB. The files are Sysprep.exe and Setupcl.exe.
With the old motherboard still intact:
You run sysprep and "RESEAL" Windows XP.
Then you put the new board in, and it re-activates Windows XP and populates the device manager list.
You do need to re-activate with the same key-code, and if you exhaust that number of activations, it will prompt you to call
Microsoft and you get a new release key at no cost from them over the phone.
If you have hardware conflicts with the new motherboard and any device, you will have extensive problems noticeable by memory dumps.
For detailed info. go to :
http://support.microsoft.com/default.aspx?scid=kb;en-us;q302577