Google these words -> "Change motherboard and save XP Operating System"
And about the OEM code. OEM versions are locked down and it would be proper for such troubles. Same thing about activation of OEM after such a change. I would be duplicating the web if I wrote more. Fix? A fresh install of a non-OEM version.
I had to change my MB and video card extra extra. I am using the same HDs. It took my a bit to make XP activated, but have succeeded. The problem that has occurred is that I can not install anything. That means vedeo and sound drivers and utilities, upgrading and updating current programs, updating WinXP, etc. The best I can figure is that I may have the old drivers that are causing a problem or that I have HD issues (although I have done several defrags and run HD bad sector tests that show nothing) or there is an XP issue taht is blocking all updates that came from my previous attempts at getting activated. (was using an OEM code that it would not except before I gave my good code which took quite a few tries because of video issues not allow activation window to run properly). Because the only CD I have is a Ghost OEM pre SP1 CD repairing via CD is out of the question. I am using Comodo Firewall (which even when disabled is still not helping installing) and Avira AV which has never giving me installation trouble before.