NOTE, force activation by: %systemroot%\system32\oobe\msoobe.exe /a
Q. How can I avoid having to reactivate my Windows XP installation
when I reinstall the OS on my machine?
A. If you plan to reinstall XP on the same hardware, you can back up
the activation status and then restore it after you reinstall the OS.
To save the activation status, back up the wpa.dbl file from the
%systemroot%\system32 folder to a disk or other location.
After you reinstall the OS, perform the following steps:
Start your Windows installation in Minimal Safe mode.
Move to the \%systemroot%\system32 folder.
Rename wpa.dbl to wpa.noact.
Copy your backed up wpa.dbl file to the system32 folder.
Reboot your system as usual.
This procedure isn't a hack to avoid activating installations and will
work only on the same hardware for an XP installation that you've
NOTE: Vista Business OEM can be downgraded to XP Pro with the Telephone option (phone call to Microsoft)