It's this simple. HP cut a deal with Microsoft for a low cost license for XP. To lock the license to the machine, the board is unique in some way that only HP boards are.
To fix this, replace it with the HP same board.
Nothing nefarious going on here, just how the licenses work.
Had to replace Mainboard on HP Pavilion. Involved re-install of windows. I used one of my XP home disks, and used a windows XP product key from one of the other computers to complete the install since the Product key form the side of the HP was ''invalid''. Now I want to Activate windows with the correct Product Key which is "invalid". Tech calls reveal:
Microsoft tech says they don't support OEM windows. HP Tech told me to take the computer to a HP repair (like staples) and the new Mainboard would have to be
''Tattooed''. Then I could use the restore disk(with the OEM windows XP home) to reinstall with the HP key.
What is Tattooed? and can I do this myself?