Also from an article I found:
"Hto preserve XP's activation status when doing a reinstallation
When you activate Windows XP, Microsoft stores the data in the Windows Product Activation database files wpa.dbl and Wpa.bak in the folder %systemroot%system32. If you change the motherboard or make significant hardware changes, XP will require you to reactive. But if you plan to reinstall XP on the same hardware, you can back up the activation status and then restore it after you reinstall and avoid the activation process. You can backup the Windows Product Activation database files to diskette. They are very small. A directory listing from my XP Pro workstation:
Volume in drive C has no label.
Volume Serial Number is 8447-0571
Directory of C:WINDOWSsystem32
10/24/2001 08:28 PM 12,584 wpa.bak
01/14/2002 09:05 AM 12,642 wpa.dbl
After you reinstall XP, to restore the Windows Product Activation database files:
Start XP to Minimal Safe mode
Change directory to the %systemroot%system32 folder
Rename the newly created wpa.dbl to wpa.nonactivated and wpa.bak, if it exists, to wpabak.nonactivated.
Copy your backed up wpa.dbl and wpb.bak files to the system32 folder
HINT No. 3: It is valuable to back up the two files WPA.DBL and WPA.BAK from the Windows\System32 folder.Then, should they get damaged, or should you do a ‘Repair’ reinstallation of Win XP, these files can be copied back to restore the prior activation status. However, this only works in those limited circumstances. The contents of these two files is matched to the specific Windows setup; therefore, contrary to what many journalists and members of the user community have written in recent months, restoring these files will not restore your activation status following a reformat and clean install."
Edited by garmanma, 28 April 2008 - 04:13 PM.