How to preserve Windows Activation through a repair operation.
Create an Activation Status Floppy Diskette
Navigate to %systemroot%\system32 folder.
Copy the wpa.dbl and wpa.bak files to the floppy diskette.
Reinstall or repair Windows XP.
Reinstall or repair normally.
After the install or repair is completed and the XP
Out Of Box Experience (OOBE) appears where you'd
normally activate the product, decline to activate
and let the installation complete.
Activate the XP Reinstallation
Restart the computer and use the F8 key to bring up the Advanced Boot
Options menu.
Select Minimal Safe Mode using Up and Down Arrow Keys and press Enter.
Navigate to %systemroot%\system32 folder.
Rename the existing wpa.dbl and wpa.bak files.
Using the floppy diskette, copy the previously backed up wpa.dbl and
wpa.bak files to the
%systemroot%\system32 folder.